Fix Spring Framework 7 compatibility issues

Fixes #22368

Author: jwalter

modules/openapi-generator/src/main/resources/kotlin-client/libraries/jvm-spring-restclient/infrastructure/ApiClient.kt.mustache

@@ -10,7 +10,7 @@ import org.springframework.util.LinkedMultiValueMap
 
 {{^nonPublicApi}}{{#explicitApi}}public {{/explicitApi}}{{/nonPublicApi}}open class ApiClient(protected val client: RestClient) {
 
-    protected inline fun <reified I : Any, reified T: Any?> request(requestConfig: RequestConfig<I>): ResponseEntity<T> {
+    protected inline fun <reified I : Any, reified T: Any> request(requestConfig: RequestConfig<I>): ResponseEntity<T> {
         return prepare(defaults(requestConfig))
             .retrieve()
             .toEntity(object : ParameterizedTypeReference<T>() {})

modules/openapi-generator/src/main/resources/kotlin-client/libraries/jvm-spring-webclient/infrastructure/ApiClient.kt.mustache

@@ -5,14 +5,14 @@ import org.springframework.http.HttpHeaders
 import org.springframework.http.HttpMethod
 import org.springframework.http.MediaType
 import org.springframework.web.reactive.function.client.WebClient
-import org.springframework.http.ResponseEntity
+import org.springframework.http.ResponseEntitypom
 import org.springframework.http.client.MultipartBodyBuilder
 import org.springframework.util.LinkedMultiValueMap
 import reactor.core.publisher.Mono
 
 {{^nonPublicApi}}{{#explicitApi}}public {{/explicitApi}}{{/nonPublicApi}}open class ApiClient(protected val client: WebClient) {
 
-    protected inline fun <reified I : Any, reified T: Any?> request(requestConfig: RequestConfig<I>): Mono<ResponseEntity<T>> {
+    protected inline fun <reified I : Any, reified T: Any> request(requestConfig: RequestConfig<I>): Mono<ResponseEntity<T>> {
         return prepare(defaults(requestConfig))
             .retrieve()
             .toEntity(object : ParameterizedTypeReference<T>() {})