Updated text list of "ignored by default" codes

Author: IanLee1521

docs/intro.rst

@@ -408,8 +408,8 @@ This is the current list of error and warning codes:
 
 
 **(*)** In the default configuration, the checks **E121**, **E123**, **E126**,
-**E133**, **E226**, **E241**, **E242** and **E704** are ignored because they
-are not rules unanimously accepted, and `PEP 8`_ does not enforce them.  The
+**E133**, **E226**, **E241**, **E242**, **E704** and **W503** are ignored because
+they are not rules unanimously accepted, and `PEP 8`_ does not enforce them.  The
 check **E133** is mutually exclusive with check **E123**.  Use switch ``--hang-
 closing`` to report **E133** instead of **E123**.