Revert "Merge branch 'jivl-fix-focused-links-missing-underline' into 'master'"

This reverts merge request !19873

app/assets/stylesheets/bootstrap_migration.scss

@@ -89,11 +89,6 @@ a {
   color: $gl-link-color;
 }
 
-a:not(.btn):focus,
-a:not(.btn):active {
-  text-decoration: underline;
-}
-
 hr {
   overflow: hidden;
 }

app/assets/stylesheets/framework/contextual_sidebar.scss

@@ -193,7 +193,6 @@
       &:focus {
         background: $link-active-background;
         color: $gl-text-color;
-        text-decoration: none;
       }
     }