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/pl.yml

@@ -541,8 +541,6 @@ pl:
     directory: Katalog profilów
     explanation: Poznaj profile na podstawie zainteresowań
     explore_mastodon: Odkrywaj %{title}
-    most_popular: Napopularniejsi
-    most_recently_active: Ostatnio aktywni
     people:
       few: "%{count} osoby"
       many: "%{count} osób"