This reverts a part of changes introduced by https://github.com/discourse/discourse/pull/13947
In that PR I:
1. Disallowed topic feature links for TL-0 users
2. Additionally, disallowed just putting any URL in topic titles for TL-0 users
Actually, we don't need the second part. It introduced unnecessary complexity for no good reason. In fact, it tries to do the job that anti-spam plugins (like Akismet plugin) should be doing.
This PR reverts this second change.