Bump com.graphql-java-kickstart:graphql-spring-boot-starter

Bumps [com.graphql-java-kickstart:graphql-spring-boot-starter](https://github.com/graphql-java-kickstart/graphql-spring-boot) from 11.0.0 to 15.0.0.
- [Release notes](https://github.com/graphql-java-kickstart/graphql-spring-boot/releases)
- [Commits](https://github.com/graphql-java-kickstart/graphql-spring-boot/compare/v11.0.0...v15.0.0)

---
updated-dependencies:
- dependency-name: com.graphql-java-kickstart:graphql-spring-boot-starter
  dependency-type: direct:production
  update-type: version-update:semver-major
...
Signed-off-by: Ndependabot[bot] <support@github.com>

plugins/gradle/example-client/build.gradle

@@ -16,7 +16,7 @@ dependencies {
     implementation "org.springframework.boot:spring-boot-starter-web:2.7.10"
     implementation "org.springframework.boot:spring-boot-starter-data-mongodb:2.7.10"
 
-    implementation "com.graphql-java-kickstart:graphql-spring-boot-starter:11.0.0"
+    implementation "com.graphql-java-kickstart:graphql-spring-boot-starter:15.0.0"
     implementation "com.graphql-java-kickstart:graphiql-spring-boot-starter:11.1.0"
     implementation "com.graphql-java:graphql-java-extended-scalars:20.0"