Fix email template css for project moved emails

app/views/notify/project_was_moved_email.html.haml

@@ -6,10 +6,10 @@
     = @project.name_with_namespace
 %p
   To update the remote url in your local repository run (for ssh):
-%p{ style: "background:$background-color; padding:10px; border:1px solid #ddd" }
+%p{ style: "background: #f5f5f5; padding:10px; border:1px solid #ddd" }
   git remote set-url origin #{@project.ssh_url_to_repo}
 %p
   or for http(s):
-%p{ style: "background:$background-color; padding:10px; border:1px solid #ddd" }
+%p{ style: "background: #f5f5f5; padding:10px; border:1px solid #ddd" }
   git remote set-url origin #{@project.http_url_to_repo}
 %br