Timeline:
* [x] Deprecate in MW 1.33
* [x] Remove uses around the codebase:
[x] MediaWiki
[x] `mediawiki.htmlform.checker`
[x] `mediawiki.page.gallery`
[x] `mediawiki.special.userlogin.signup.js`
[x] CentralNotice – `ext.centralNotice.adminUi.campaignManager`
[x] Flow – `ext.flow.components` and `ext.flow`
[x] Graph – `ext.graph.sandbox`
[x] InputBox – `ext.inputBox`
[x] Kartographer – `ext.kartographer.box` and `ext.kartographer.visualEditor`
[x] MassMessage – `ext.MassMessage.special.js`
[x] MediaViewer – `mmv`
[x] MobileFrontend – `mobile.startup`
[x] RelatedArticles – `ext.relatedArticles.readMore.bootstrap`
[x] Translate – `ext.translate.messagetable`
[x] Wikibase – `jquery.wikibase.entityselector`, `wikibase.view.ViewFactory`, and `ext.WikidataPageBanner.positionBanner`
[x] WikiEditor – `ext.wikiEditor`
[x] (skin) Vector – `skins.vector.js`
[x] (skin) MetroLook – `skins.metrolook.js`
* [x] Remove in ? MW 1.35.