Merge pull request #1259 from RDFLib/dependabot/pip/sphinx-3.5.1

Bump sphinx from 3.5.0 to 3.5.1

Author: Nicholas Car

docs/sphinx-requirements.txt

@@ -1,3 +1,3 @@
-sphinx==3.5.0
+sphinx==3.5.1
 sphinxcontrib-apidoc
 git+https://github.com/gniezen/n3pygments.git