The description of mediawiki/extensions/GitHub says that it is only used for i18n updates, but translatewiki can update extensions on github and this extensions seems to be configurated to do it, so it should be archived on gerrit:
- Remove from mediawiki/extensions ( along with in .gitmodules)
- Remove tests in integration/config ( zuul/layout.yaml )
- Archive the extension's diffusion repository: rEGIT (or point it to github? - https://github.com/JeroenDeDauw/GitHub)
- Mark the repository read-only in Gerrit: https://gerrit.wikimedia.org/r/#/admin/projects/mediawiki/extensions/GitHub
- Archive the GitHub mirror: https://github.com/wikimedia/mediawiki-extensions-GitHub