**Reason**: Code moved into #timedmediahandler in {T164037}.
- [x] Stop branching for Wikimedia production: https://gerrit.wikimedia.org/r/c/mediawiki/tools/release/+/441523
- [x] Remove from Wikimedia production: https://gerrit.wikimedia.org/r/c/operations/mediawiki-config/+/441521/
- [x] Archive documentation on `mediawiki.org` (https://www.mediawiki.org/wiki/Extension:MwEmbedSupport)
- [ ] Remove from `mediawiki/extensions` (along with in `.gitmodules`)
- [x] Remove tests in `integration/config`: https://gerrit.wikimedia.org/r/#/c/integration/config/+/443006
- [ ] Remove from `translatewiki`
- [ ] ~~Empty repository and add an `ARCHIVED` file~~ (not doing this for now per https://gerrit.wikimedia.org/r/#/c/mediawiki/extensions/MwEmbedSupport/+/350755/).
- [ ] Archive the extension's diffusion repository
- [ ] Mark the repository read-only in Gerrit
- [ ] Delete the GitHub mirror