docs: E203 also applies to comma and semicolon

Per PEP8, "Avoid extraneous whitespace ... Immediately before a comma, semicolon, or colon". https://www.python.org/dev/peps/pep-0008/#pet-peeves

Author: wjandrea

docs/intro.rst

@@ -264,7 +264,7 @@ This is the current list of error and warning codes:
 +------------+----------------------------------------------------------------------+
 | E202       | whitespace before ')'                                                |
 +------------+----------------------------------------------------------------------+
-| E203       | whitespace before ':'                                                |
+| E203       | whitespace before ',', ';', or ':'                                   |
 +------------+----------------------------------------------------------------------+
 +------------+----------------------------------------------------------------------+
 | E211       | whitespace before '('                                                |