Fix typo in DispatcherServlet Javadoc

Closes gh-23726

Author: KangZhiDong

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

@@ -255,7 +255,7 @@ public class DispatcherServlet extends FrameworkServlet {
 	public static final String FLASH_MAP_MANAGER_ATTRIBUTE = DispatcherServlet.class.getName() + ".FLASH_MAP_MANAGER";
 
 	/**
-	 * Name of request attribute that exposes an Exception resolved with an
+	 * Name of request attribute that exposes an Exception resolved with a
 	 * {@link HandlerExceptionResolver} but where no view was rendered
 	 * (e.g. setting the status code).
 	 */