Merge branch 'master' into glitch-soc/merge-upstream

Conflicts:
- app/controllers/admin/base_controller.rb
  Some refactoring made upstream, no real conflict.
- app/javascript/mastodon/features/compose/components/compose_form.js
  Updated using upstream's code but using maxChars instead of the
  hardcoded length of 500 characters per toot.
- app/javascript/styles/mastodon/components.scss
  Upstream redesigned the onboarding modal. Not sure why we had a
  conflict there.

config/locales/sk.yml

@@ -536,8 +536,6 @@ sk:
     directory: Databáza profilov
     explanation: Pátraj po užívateľoch podľa ich záujmov
     explore_mastodon: Prebádaj %{title}
-    most_popular: Najpopulárnejšie
-    most_recently_active: Naposledy aktívni
     people:
       few: "%{count} ľudia"
       one: "%{count} človek"