Fixed a typo in the HTMLParser.feed docstrings. The docstring started with an 'r', like a rawstring. (#1759)

diff --git a/Lib/html/parser.py b/Lib/html/parser.py
index ef869bc..9597948 100644
--- a/Lib/html/parser.py
+++ b/Lib/html/parser.py
@@ -102,7 +102,7 @@
         _markupbase.ParserBase.reset(self)
 
     def feed(self, data):
-        r"""Feed data to the parser.
+        """Feed data to the parser.
 
         Call this as often as you want, with as little or as much text
         as you want (may include '\n').