Move off the invisible include as bootstrap has deprecated it

Resolves https://gitlab.com/gitlab-org/gitlab/-/issues/246747

app/assets/stylesheets/pages/issues.scss

@@ -294,12 +294,12 @@ ul.related-merge-requests > li {
 
       &::after {
         content: image-url('icon_anchor.svg');
-        @include invisible(hidden);
+        visibility: hidden;
       }
     }
 
     &:hover > a.anchor::after {
-      @include invisible(visible);
+      visibility: visible;
     }
   }
 }