Merge commit 'd13d7b4566d551d027830f7dfc987ba3a8e2dd4f' into glitch-soc/merge-upstream

Conflicts are too numerous to list, but they are all caused by upstream's
theming changes and all have to do with the differences between upstream and
glitch-soc in the theming systems.

They were all manually resolved by adapting the relevant code.

config/locales/en.yml

@@ -2022,10 +2022,7 @@ en:
     review_link: Review terms of service
     title: The terms of service of %{domain} are changing
   themes:
-    contrast: Mastodon (High contrast)
-    default: Mastodon (Dark)
-    mastodon-light: Mastodon (Light)
-    system: Automatic (use system theme)
+    default: Mastodon
   time:
     formats:
       default: "%b %d, %Y, %H:%M"

config/settings.yml

@@ -20,7 +20,7 @@ defaults: &defaults
   preview_sensitive_media: false
   noindex: false
   flavour: 'glitch'
-  skin: 'system'
+  skin: 'default'
   trends: true
   trendable_by_default: false
   trending_status_cw: true