Fix library generation compatibility with Gradle 7.2 (#10716)

* Make Java libraries compatible with Gradle 7

* Make kotlin-spring compatible with Gradle 7

* Update samples to comply to Gradle 7.2

* Generate samples

samples/server/petstore/kotlin-springboot-reactive/build.gradle.kts

@@ -2,8 +2,7 @@ import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
 
 buildscript {
     repositories {
-        jcenter()
-        maven { url = uri("https://repo1.maven.org/maven2") }
+        mavenCentral()
     }
     dependencies {
         classpath("org.springframework.boot:spring-boot-gradle-plugin:2.2.0.M3")
@@ -14,8 +13,7 @@ group = "org.openapitools"
 version = "1.0.0"
 
 repositories {
-    jcenter()
-    maven { url = uri("https://repo1.maven.org/maven2") }
+    mavenCentral()
 }
 
 tasks.withType<KotlinCompile> {