Fix ResourceHttpRequestHandler#setHeaders JavaDoc

Closes gh-35004
Signed-off-by: 秦利斌 <68638598+Allan-QLB@users.noreply.github.com>

spring-webmvc/src/main/java/org/springframework/web/servlet/resource/ResourceHttpRequestHandler.java

@@ -728,7 +728,7 @@ public class ResourceHttpRequestHandler extends WebContentGenerator
 	 * Called for GET requests as well as HEAD requests.
 	 * @param response current servlet response
 	 * @param resource the identified resource (never {@code null})
-	 * @param mediaType the resource's media type (never {@code null})
+	 * @param mediaType the resource's media type
 	 * @throws IOException in case of errors while setting the headers
 	 */
 	protected void setHeaders(HttpServletResponse response, Resource resource, @Nullable MediaType mediaType)