Merge branch 'mg-fix-select2-assets' into 'master'

Fix broken select2 assets

See merge request gitlab-org/gitlab!39853

app/assets/stylesheets/application.scss

@@ -13,7 +13,7 @@
 // directory.
 @import '@gitlab/at.js/dist/css/jquery.atwho';
 @import 'dropzone/dist/basic';
-@import 'select2/select2';
+@import 'select2';
 
 // GitLab UI framework
 @import 'framework';