update java samples

samples/client/petstore/java/okhttp-gson-nullable-required/api/openapi.yaml

@@ -101,7 +101,7 @@ paths:
       summary: Finds Pets by status
       tags:
       - pet
-      x-accepts: application/json
+      x-accepts: "application/json,application/xml"
   /pet/findByTags:
     get:
       deprecated: true
@@ -141,7 +141,7 @@ paths:
       summary: Finds Pets by tags
       tags:
       - pet
-      x-accepts: application/json
+      x-accepts: "application/json,application/xml"
   /pet/{petId}:
     delete:
       description: ""
@@ -206,7 +206,7 @@ paths:
       summary: Find pet by ID
       tags:
       - pet
-      x-accepts: application/json
+      x-accepts: "application/json,application/xml"
     post:
       description: ""
       operationId: updatePetWithForm
@@ -319,7 +319,7 @@ paths:
       tags:
       - store
       x-content-type: application/json
-      x-accepts: application/json
+      x-accepts: "application/json,application/xml"
   /store/order/{orderId}:
     delete:
       description: For valid response try integer IDs with value < 1000. Anything
@@ -376,7 +376,7 @@ paths:
       summary: Find purchase order by ID
       tags:
       - store
-      x-accepts: application/json
+      x-accepts: "application/json,application/xml"
   /user:
     post:
       description: This can only be done by the logged in user.
@@ -490,7 +490,7 @@ paths:
       summary: Logs user into the system
       tags:
       - user
-      x-accepts: application/json
+      x-accepts: "application/json,application/xml"
   /user/logout:
     get:
       description: ""
@@ -557,7 +557,7 @@ paths:
       summary: Get user by user name
       tags:
       - user
-      x-accepts: application/json
+      x-accepts: "application/json,application/xml"
     put:
       description: This can only be done by the logged in user.
       operationId: updateUser