Merge branch '10535-buttons-css' into 'master'

Removes EE differences for buttons.scss

Closes gitlab-ee#10535

See merge request gitlab-org/gitlab-ce!26358

app/assets/stylesheets/framework/buttons.scss

@@ -443,7 +443,8 @@
     border-color: transparent;
   }
 
-  &.btn-secondary-hover-link {
+  &.btn-secondary-hover-link,
+  &.btn-default-hover-link {
     color: $gl-text-color-secondary;
 
     &:hover,