[Java] rename x-contentType to x-content-type (#11895)

* rename x-contentType to x-content-type

* undo changes

samples/server/petstore/springboot-beanvalidation-no-nullable/src/main/resources/openapi.yaml

@@ -46,7 +46,7 @@ paths:
       tags:
       - pet
       x-codegen-request-body-name: body
-      x-contentType: application/json
+      x-content-type: application/json
       x-accepts: application/json
       x-tags:
       - tag: pet
@@ -83,7 +83,7 @@ paths:
       tags:
       - pet
       x-codegen-request-body-name: body
-      x-contentType: application/json
+      x-content-type: application/json
       x-accepts: application/json
       x-tags:
       - tag: pet
@@ -280,7 +280,7 @@ paths:
       summary: Updates a pet in the store with form data
       tags:
       - pet
-      x-contentType: application/x-www-form-urlencoded
+      x-content-type: application/x-www-form-urlencoded
       x-accepts: application/json
       x-tags:
       - tag: pet
@@ -321,7 +321,7 @@ paths:
       summary: uploads an image
       tags:
       - pet
-      x-contentType: multipart/form-data
+      x-content-type: multipart/form-data
       x-accepts: application/json
       x-tags:
       - tag: pet
@@ -374,7 +374,7 @@ paths:
       tags:
       - store
       x-codegen-request-body-name: body
-      x-contentType: '*/*'
+      x-content-type: '*/*'
       x-accepts: application/json
       x-tags:
       - tag: store
@@ -458,7 +458,7 @@ paths:
       tags:
       - user
       x-codegen-request-body-name: body
-      x-contentType: '*/*'
+      x-content-type: '*/*'
       x-accepts: application/json
       x-tags:
       - tag: user
@@ -482,7 +482,7 @@ paths:
       tags:
       - user
       x-codegen-request-body-name: body
-      x-contentType: '*/*'
+      x-content-type: '*/*'
       x-accepts: application/json
       x-tags:
       - tag: user
@@ -506,7 +506,7 @@ paths:
       tags:
       - user
       x-codegen-request-body-name: body
-      x-contentType: '*/*'
+      x-content-type: '*/*'
       x-accepts: application/json
       x-tags:
       - tag: user
@@ -652,7 +652,7 @@ paths:
       tags:
       - user
       x-codegen-request-body-name: body
-      x-contentType: '*/*'
+      x-content-type: '*/*'
       x-accepts: application/json
       x-tags:
       - tag: user
@@ -680,7 +680,7 @@ paths:
       tags:
       - fake_classname_tags 123#$%^
       x-codegen-request-body-name: body
-      x-contentType: application/json
+      x-content-type: application/json
       x-accepts: application/json
       x-tags:
       - tag: fake_classname_tags 123#$%^
@@ -835,7 +835,7 @@ paths:
       summary: To test enum parameters
       tags:
       - fake
-      x-contentType: application/x-www-form-urlencoded
+      x-content-type: application/x-www-form-urlencoded
       x-accepts: application/json
       x-tags:
       - tag: fake
@@ -860,7 +860,7 @@ paths:
       tags:
       - fake
       x-codegen-request-body-name: body
-      x-contentType: application/json
+      x-content-type: application/json
       x-accepts: application/json
       x-tags:
       - tag: fake
@@ -963,7 +963,7 @@ paths:
          가짜 엔드 포인트
       tags:
       - fake
-      x-contentType: application/x-www-form-urlencoded
+      x-content-type: application/x-www-form-urlencoded
       x-accepts: application/json
       x-tags:
       - tag: fake
@@ -988,7 +988,7 @@ paths:
       tags:
       - fake
       x-codegen-request-body-name: body
-      x-contentType: '*/*'
+      x-content-type: '*/*'
       x-accepts: '*/*'
       x-tags:
       - tag: fake
@@ -1013,7 +1013,7 @@ paths:
       tags:
       - fake
       x-codegen-request-body-name: body
-      x-contentType: '*/*'
+      x-content-type: '*/*'
       x-accepts: '*/*'
       x-tags:
       - tag: fake
@@ -1038,7 +1038,7 @@ paths:
       tags:
       - fake
       x-codegen-request-body-name: body
-      x-contentType: '*/*'
+      x-content-type: '*/*'
       x-accepts: '*/*'
       x-tags:
       - tag: fake
@@ -1063,7 +1063,7 @@ paths:
       tags:
       - fake
       x-codegen-request-body-name: body
-      x-contentType: '*/*'
+      x-content-type: '*/*'
       x-accepts: '*/*'
       x-tags:
       - tag: fake
@@ -1092,7 +1092,7 @@ paths:
       summary: test json serialization of form data
       tags:
       - fake
-      x-contentType: application/x-www-form-urlencoded
+      x-content-type: application/x-www-form-urlencoded
       x-accepts: application/json
       x-tags:
       - tag: fake
@@ -1116,7 +1116,7 @@ paths:
       tags:
       - fake
       x-codegen-request-body-name: param
-      x-contentType: application/json
+      x-content-type: application/json
       x-accepts: application/json
       x-tags:
       - tag: fake
@@ -1142,7 +1142,7 @@ paths:
       tags:
       - fake
       x-codegen-request-body-name: body
-      x-contentType: application/json
+      x-content-type: application/json
       x-accepts: application/json
       x-tags:
       - tag: fake
@@ -1180,7 +1180,7 @@ paths:
       tags:
       - fake
       x-codegen-request-body-name: XmlItem
-      x-contentType: application/xml
+      x-content-type: application/xml
       x-accepts: application/json
       x-tags:
       - tag: fake
@@ -1206,7 +1206,7 @@ paths:
       tags:
       - $another-fake?
       x-codegen-request-body-name: body
-      x-contentType: application/json
+      x-content-type: application/json
       x-accepts: application/json
       x-tags:
       - tag: $another-fake?
@@ -1228,7 +1228,7 @@ paths:
       tags:
       - fake
       x-codegen-request-body-name: body
-      x-contentType: application/json
+      x-content-type: application/json
       x-accepts: application/json
       x-tags:
       - tag: fake
@@ -1328,7 +1328,7 @@ paths:
       summary: uploads an image (required)
       tags:
       - pet
-      x-contentType: multipart/form-data
+      x-content-type: multipart/form-data
       x-accepts: application/json
       x-tags:
       - tag: pet