refresh docs badge

Author: mttk

README.rst

@@ -4,7 +4,7 @@
 .. image:: https://codecov.io/gh/pytorch/text/branch/master/graph/badge.svg
     :target: https://codecov.io/gh/pytorch/text
 
-.. image:: https://readthedocs.org/projects/torchtext/badge/?version=latest
+.. image:: http://readthedocs.org/projects/torchtext/badge/?version=latest
     :target: http://torchtext.readthedocs.io/en/latest/?badge=latest
 
 torchtext