Fix the subtitle for the AbuseFilter history view

The html was wrongly escaped. Also append it to the
existing one to leave the navigation in place.

See the subtitle on:
https://en.wikipedia.org/wiki/Special:AbuseFilter/history/?user=Foo

Change-Id: I5725fe15eda1a48fd313c6394800e8b92c450d9d
Merge "Fix the subtitle for the AbuseFilter history view"