Don't hardcode that templates are never disambiguation pages

There's no reason why they couldn't be, and this makes extending this
code harder. If they're not supposed to, then that should be solved
on-wiki by wrapping the __DISAMBIG__ in <includeonly/>.

Change-Id: I20ad2e20301cb32733f510662c2d173cfbda869a
Merge "Don't hardcode that templates are never disambiguation pages"