Fix checkstyle violation

Author: rstoyanchev

spring-webmvc/src/main/java/org/springframework/web/servlet/handler/HandlerMappingIntrospector.java

@@ -332,7 +332,8 @@ private static CachedResult getAttribute(HttpServletRequest request) {
 	 * for a given request identified by dispatcher type and requestURI.
 	 * @since 6.0.14
 	 */
-	public final static class CachedResult {
+	@SuppressWarnings("serial")
+	public static final class CachedResult {
 
 		private final DispatcherType dispatcherType;