Merge branch '39001-mr-tabs-hover' into 'master'

Fixes from CSS refactor

Closes #39001 and #38939

See merge request gitlab-org/gitlab-ce!14828

app/assets/stylesheets/framework/secondary-navigation-elements.scss

@@ -6,6 +6,7 @@
   margin: 0;
   list-style: none;
   height: auto;
+  border-bottom: 1px solid $border-color;
 
   li {
     display: flex;
@@ -24,6 +25,7 @@
       &:focus {
         text-decoration: none;
         color: $black;
+        border-bottom: 2px solid $gray-darkest;
 
         .badge {
           color: $black;