Revert "482055 - Increase visibility of ServletHandler.notFound() to public"

This reverts commit 53663543767d6b4ae1e6084ae7199e776195b17e.
diff --git a/jetty-servlet/src/main/java/org/eclipse/jetty/servlet/ServletHandler.java b/jetty-servlet/src/main/java/org/eclipse/jetty/servlet/ServletHandler.java
index 4ae4925..ca2f2e5 100644
--- a/jetty-servlet/src/main/java/org/eclipse/jetty/servlet/ServletHandler.java
+++ b/jetty-servlet/src/main/java/org/eclipse/jetty/servlet/ServletHandler.java
@@ -1374,7 +1374,7 @@
     }
 
     /* ------------------------------------------------------------ */
-    public void notFound(HttpServletRequest request,
+    protected void notFound(HttpServletRequest request,
                   HttpServletResponse response)
         throws IOException
     {