Remove suggested approvers text decoration on hover

What does this MR do?

This regressed when we began using the mr_widget_author component in the mr widget. At some point, it will make sense to use the user avatar link component here. But for a quick fix, I'm just applying text-decoration:none to override the default applied to all a tags on hover.

Before

After

What are the relevant issue numbers?

Closes https://gitlab.com/gitlab-org/gitlab-ee/issues/2607