[Kotlin][Spring] fix build.gradle.kts and pom.xml for SpringBoot 2.x

[pstorch]

SpringBoot 2.x still uses javax namespace, but the build files build.gradle.kts and pom.xml where generated with the newer jakarta.validation and jakarta.annotation dependencies resulting in build errors.

Example build error:

~/git/openapi-generator/samples/server/petstore/kotlin-springboot-delegate> gradle build

> Task :compileKotlin FAILED
e: /home/peter/git/openapi-generator/samples/server/petstore/kotlin-springboot-delegate/src/main/kotlin/org/openapitools/api/PetApiController.kt: (7, 19): Unresolved reference: Generated
e: /home/peter/git/openapi-generator/samples/server/petstore/kotlin-springboot-delegate/src/main/kotlin/org/openapitools/api/PetApiDelegate.kt: (18, 19): Unresolved reference: Generated
e: /home/peter/git/openapi-generator/samples/server/petstore/kotlin-springboot-delegate/src/main/kotlin/org/openapitools/api/StoreApiController.kt: (7, 19): Unresolved reference: Generated
e: /home/peter/git/openapi-generator/samples/server/petstore/kotlin-springboot-delegate/src/main/kotlin/org/openapitools/api/StoreApiDelegate.kt: (17, 19): Unresolved reference: Generated
e: /home/peter/git/openapi-generator/samples/server/petstore/kotlin-springboot-delegate/src/main/kotlin/org/openapitools/api/UserApiController.kt: (7, 19): Unresolved reference: Generated
e: /home/peter/git/openapi-generator/samples/server/petstore/kotlin-springboot-delegate/src/main/kotlin/org/openapitools/api/UserApiDelegate.kt: (17, 19): Unresolved reference: Generated

FAILURE: Build failed with an exception.

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