Merge commit 'bec6a1cad4c509c53deb378c7ba984ba7e2de5a9' into glitch-soc/merge-upstream

Conflicts:
- `app/controllers/auth/confirmations_controller.rb`:
  Upstream merged our captcha code, but there are some
  conflicts due to glitch-soc's theming system.
- `app/views/admin/settings/registrations/show.html.haml`:
  Upstream merged our captcha code, but there are some
  conflicts due to glitch-soc's theming system.

Additional changes:
- `Gemfile`:
  Upstream added hcaptcha dependency in another place in the file.
- `config/settings.yml`:
  Upstream added the `captcha_enabled` setting in another place in the file.

app/javascript/styles/mastodon/forms.scss

@@ -136,6 +136,10 @@ code {
     line-height: 22px;
     color: $secondary-text-color;
     margin-bottom: 30px;
+
+    a {
+      color: $highlight-text-color;
+    }
   }
 
   .rules-list {
@@ -1039,6 +1043,10 @@ code {
   }
 }
 
+.simple_form .h-captcha {
+  text-align: center;
+}
+
 .permissions-list {
   &__item {
     padding: 15px;