Fix styling of merge request dropdown badge styles

The styles for the dropdown badges went incorrect when
startup CSS was enabled by default.
This fixes this by including the correct CSS to match
the application stylesheet.

app/assets/stylesheets/startup/startup-general.scss

@@ -1163,8 +1163,8 @@ input {
   line-height: 18px;
   margin: 4px 0 4px 2px;
 }
-.title-container .badge.badge-pill,
-.navbar-nav .badge.badge-pill {
+.title-container .badge.badge-pill:not(.merge-request-badge),
+.navbar-nav .badge.badge-pill:not(.merge-request-badge) {
   position: inherit;
   font-weight: 400;
   margin-left: -6px;