specials: Use username from query on Special:ProtectedPages

The query includes the username of the protector via actor_name, use
this name for the LinkBatch instead of an extra query to resolve the
userid to username via UserCache.

The userid query was needed before the actor migration to ensure renamed
user are loaded/displayed correctly (UserCache was used before
83e184670c to display the username).

Change-Id: I23c72482008f3f4d1dae85c3308e7b6cd4981fbb