Fix Flow entries in Special:EditWatchlist

This will do 2 things:
* Remove the link to the talk page (which is irrelevant for Flow topics)
* Change Topic:<uuid> to the content of the topic title

However, even without that change, this will still work.
(but we should probably just wait for the core change to get in first)

In a follow-up commit, I'll also batch-load all the data beforehand.

Change-Id: If206aa295480b5c074640541e109811c6022c016