**Reason**: Per @ashley's comments:
>>! In T153385#3404294, @ashley wrote:
> Given the existence of Florian's awesome [[https://www.mediawiki.org/wiki/Extension:OOJsUIAjaxLogin|OOJsUIAjaxLogin extension]], which actually works, looks modern and isn't a horrible pile of hacks on top of hacks, I'm going to say that AjaxLogin is deprecated in favor of OOJsUIAjaxLogin and thus I'm declining this task.
- [x] Archive documentation on `mediawiki.org` - https://www.mediawiki.org/wiki/Extension:AjaxLogin ( done by @Kghbln )
- [x] Remove from `mediawiki/extensions`
- [x] Remove tests in `intregation/config` ( `zuul/layout.yaml` )
- [x] Remove from `translatewiki` ( `groups/MediaWiki/mediawiki-extensions.txt` )
- [x] Mark as read-only on Gerrit ( https://gerrit.wikimedia.org/r/#/admin/projects/mediawiki/extensions/AjaxLogin )
- [x] Archive Phabricator project #mediawiki-extensions-ajaxlogin for associated extension/skin ( done [[https://phabricator.wikimedia.org/project/manage/406/#37258|here]] )
- [x] Edit Phabricator project #mediawiki-extensions-ajaxlogin description for associated extension/skin with a link to this ticket ( done [[https://phabricator.wikimedia.org/project/manage/406/#37254|here]] )
- [ ] Archive the extension's diffusion repository: ( https://phabricator.wikimedia.org/r/project/mediawiki/extensions/AjaxLogin )