Cast torch.__version__ to string (#2062)

To squash the warnings during the build time

Author: malfet

conf.py

@@ -141,9 +141,9 @@
 # built documents.
 #
 # The short X.Y version.
-version = torch.__version__
+version = str(torch.__version__)
 # The full version, including alpha/beta/rc tags.
-release = torch.__version__
+release = str(torch.__version__)
 
 # The language for content autogenerated by Sphinx. Refer to documentation
 # for a list of supported languages.