Replace d-md-block with gitlab-ui class for project

- use gitlab-ui style wrappers

app/views/dashboard/projects/index.html.haml

@@ -5,7 +5,7 @@
 
 - if show_customize_homepage_banner?(@customize_homepage)
   = content_for :customize_homepage_banner do
-    .d-none.d-md-block{ class: "gl-pt-6! gl-pb-2! #{(container_class unless @no_container)} #{@content_class}" }
+    .gl-display-none.gl-display-md-block{ class: "gl-pt-6! gl-pb-2! #{(container_class unless @no_container)} #{@content_class}" }
       .js-customize-homepage-banner{ data: { svg_path: image_path('illustrations/monitoring/getting_started.svg'),
         preferences_behavior_path: profile_preferences_path(anchor: 'behavior'),
         callouts_path: user_callouts_path,