Fixed the formatting in the table

Author: ilam

docs/intro.rst

@@ -122,7 +122,7 @@ You can also make pep8.py show the error text in different formats by using --fo
   $ pep8 testsuite/E40.py --format='%(path)s|%(row)d|%(col)d| %(code)s %(text)s'
   testsuite/E40.py|2|10| E401 multiple imports on one line
 
-Variables in the ``custom`` format option::
+Variables in the ``custom`` format option
 
 +----------------+------------------+
 | **Variable**   | **Significance** |