Merge branch 'fix-alert-btn' into 'master'

Fix alert button styling so that they don't show up white

Closes #48407

See merge request gitlab-org/gitlab-ce!20163

app/assets/stylesheets/bootstrap_migration.scss

@@ -310,7 +310,7 @@ pre code {
   color: $white-light;
 
   h4,
-  a,
+  a:not(.btn),
   .alert-link {
     color: $white-light;
   }

changelogs/unreleased/fix-alert-btn.yml

+---
+title: Fix alert button styling so that they don't show up white
+merge_request:
+author:
+type: fixed