Merge branch 'fix-billing-style' into 'master'

Fix billing card style

Closes #6326

See merge request gitlab-org/gitlab-ee!6023

ee/app/views/shared/billings/_billing_plan.html.haml

 .card{ class: ('current' if current_plan?(plan)) }
-  .card-header
+  .card-header.bg-info
     = plan.name
 
   .card-body