docs: remove section headers from github.in

They give the impression that, for example,
third-party XBlocks belong in github.in.
In reality, GitHub-hosted requirements should be avoided
in all circumstances. Third-party XBlocks are best
added to base.in as a PyPI-hosted dependency.

Furthermore, the existing section headers are not
even being followed.

requirements/edx/github.in

@@ -63,25 +63,13 @@
 #     re-install the package each time, and can be useful when working with two
 #     repos before picking a version number. Don't use 0.0 on master, only for
 #     tight-loop work in progress.
-
-
-# Python libraries to install directly from github
-
-# Third-party:
 -e git+https://github.com/openedx/django-wiki.git@1.1.1#egg=django-wiki
 -e git+https://github.com/openedx/olxcleaner.git@2f0d6c7f126cbd69c9724b7b57a0b2565330a297#egg=olxcleaner
 git+https://github.com/openedx/MongoDBProxy.git@d92bafe9888d2940f647a7b2b2383b29c752f35a#egg=MongoDBProxy==0.1.0+edx.2
-
-# original repo is not maintained any more.
 git+https://github.com/openedx/django-require.git@0c54adb167142383b26ea6b3edecc3211822a776#egg=django-require==1.0.12
-
-# Our libraries:
 -e git+https://github.com/openedx/blockstore.git@1.2.1#egg=blockstore==1.2.1  # Note: Blockstore 1.2.2 is failing.
 -e git+https://github.com/openedx/codejail.git@3.1.3#egg=codejail==3.1.3
 -e git+https://github.com/openedx/RateXBlock.git@2.0.1#egg=rate-xblock
 -e git+https://github.com/openedx/xblock-google-drive.git@2d176468e33c0713c911b563f8f65f7cf232f5b6#egg=xblock-google-drive
-
-# Third Party XBlocks
-
 git+https://github.com/open-craft/xblock-poll@v1.12.0#egg=xblock-poll==1.12.0
 git+https://github.com/openedx/xblock-drag-and-drop-v2@v2.3.5#egg=xblock-drag-and-drop-v2==2.3.5