Remove not needed null check (#11303)

Motivation:

throw exception if there is no method, it never is null, condition is always true

Modification:

remove unnecessary condition

Result:

cleanup

transport/src/main/java/io/netty/channel/ChannelHandlerMask.java

@@ -180,7 +180,7 @@ final class ChannelHandlerMask {
                 }
                 return false;
             }
-            return m != null && m.isAnnotationPresent(Skip.class);
+            return m.isAnnotationPresent(Skip.class);
         });
     }