fix Api Interface for kotlin-spring with spring-cloud library (#19877)

Author: pstorch

modules/openapi-generator/src/main/resources/kotlin-spring/apiInterface.mustache

@@ -52,7 +52,9 @@ import kotlinx.coroutines.flow.Flow
 import kotlin.collections.List
 import kotlin.collections.Map
 
+{{^useFeignClient}}
 @RestController
+{{/useFeignClient}}
 {{#useBeanValidation}}
 @Validated
 {{/useBeanValidation}}

samples/server/petstore/kotlin-spring-cloud/src/main/kotlin/org/openapitools/api/PetApi.kt

@@ -29,7 +29,6 @@ import javax.validation.Valid
 import kotlin.collections.List
 import kotlin.collections.Map
 
-@RestController
 @Validated
 interface PetApi {
 

samples/server/petstore/kotlin-spring-cloud/src/main/kotlin/org/openapitools/api/StoreApi.kt

@@ -28,7 +28,6 @@ import javax.validation.Valid
 import kotlin.collections.List
 import kotlin.collections.Map
 
-@RestController
 @Validated
 interface StoreApi {
 

samples/server/petstore/kotlin-spring-cloud/src/main/kotlin/org/openapitools/api/UserApi.kt

@@ -28,7 +28,6 @@ import javax.validation.Valid
 import kotlin.collections.List
 import kotlin.collections.Map
 
-@RestController
 @Validated
 interface UserApi {