Merge pull request readthedocs#83 from readthedocs/pyup/scheduled-update-2020-07-27

pyup:  Scheduled weekly dependency update for week 30

Author: humitos

docs/requirements.txt

@@ -4,5 +4,5 @@ sphinx-rtd-theme==0.5.0
 sphinx-tabs==1.1.13
 sphinx-prompt==1.1.0
 sphinx-version-warning==1.1.2
-sphinx-notfound-page==0.4
+sphinx-notfound-page==0.5
 sphinx-autobuild==0.7.1