rel(0.4.0rc1): do not pin URLs in setup.cfg

Removing the URL links for sphinxcontrib extensions, since they do not
affect the package distribution but invalidate it for upload to pypi.

We are now building the docs on circleci and using the package pins
indicated by ``docs/requirements.txt`` - we should be fine doing this
in this instance.

setup.cfg

@@ -53,8 +53,8 @@ doc =
     sphinx-argparse
     sphinx_rtd_theme
     sphinxcontrib-apidoc ~= 0.3.0
-    sphinxcontrib-napoleon @ git+https://github.com/AleksandarPetrov/napoleon.git@0dc3f28a309ad602be5f44a9049785a1026451b3
-    sphinxcontrib-versioning @ git+https://github.com/rwblair/sphinxcontrib-versioning.git@39b40b0b84bf872fc398feff05344051bbce0f63
+    sphinxcontrib-napoleon
+    sphinxcontrib-versioning
 docs =
     %(doc)s
 duecredit = duecredit