Add missing @⁠Override annotations

... and suppress "serial" warnings

spring-web/src/test/java/org/springframework/web/client/support/RestClientProxyRegistryIntegrationTests.java

@@ -117,6 +117,7 @@ public class RestClientProxyRegistryIntegrationTests {
 	void beansAreCreatedUsingBeanClassLoader() {
 		ClassLoader beanClassLoader = new OverridingClassLoader(getClass().getClassLoader()) {
 
+			@Override
 			protected boolean isEligibleForOverriding(String className) {
 				return className.contains("EchoA");
 			};

spring-web/src/test/java/org/springframework/web/context/request/async/WebAsyncManagerTests.java

@@ -137,6 +137,7 @@ class WebAsyncManagerTests {
 	}
 
 	@Test // gh-30232
+	@SuppressWarnings("serial")
 	void startCallableProcessingSubmitException() throws Exception {
 		RuntimeException ex = new RuntimeException();
 

spring-web/src/test/java/org/springframework/web/filter/OncePerRequestFilterTests.java

@@ -50,6 +50,7 @@ class OncePerRequestFilterTests {
 
 
 	@BeforeEach
+	@SuppressWarnings("serial")
 	public void setup() throws Exception {
 		this.request = new MockHttpServletRequest();
 		this.request.setScheme("http");