Update README.rst
Update README.rst

Fixed `README.rst's` `code-block` directive `lang` name typo.
mozillazg/redis-py-doc,mozillazg/redis-py-doc,andymccurdy/redis-py,andymccurdy/redis-py,redis/redis-py,5977862/redis-py,alisaifee/redis-py,redis/redis-py,5977862/redis-py,5977862/redis-py,alisaifee/redis-py,andymccurdy/redis-py