Merge branch 'winh-merge-request-version-dropdowns' into 'master'

Make merge request version dropdowns consistent

See merge request !13590

app/assets/stylesheets/pages/merge_requests.scss

@@ -612,6 +612,8 @@
 }
 
 .mr-version-controls {
+  @include new-style-dropdown;
+
   position: relative;
   background: $gray-light;
   color: $gl-text-color;