Reason: Code moved into TimedMediaHandler in T164037: Move all the code out of MwEmbedSupport and into TimedMediaHandler, its only user.
- Stop branching for Wikimedia production: https://gerrit.wikimedia.org/r/c/mediawiki/tools/release/+/441523
- Remove from Wikimedia production: https://gerrit.wikimedia.org/r/c/operations/mediawiki-config/+/441521/
- Archive documentation on mediawiki.org (https://www.mediawiki.org/wiki/Extension:MwEmbedSupport)
- Remove tests in integration/config: https://gerrit.wikimedia.org/r/#/c/integration/config/+/443006
- Remove from translatewiki: https://gerrit.wikimedia.org/r/#/c/translatewiki/+/444937
- Remove from mediawiki/extensions (along with in .gitmodules)
Todo later (not doing this for now):
- Empty repository and add an ARCHIVED file
- Archive the extension's Diffusion repository
- Mark the repository read-only in Gerrit
- Delete the GitHub mirror
- Archive Phabricator project MediaWiki-extensions-MwEmbedSupport for associated extension/skin and edit its description for associated extension/skin with a link to this ticket