This patch fixes Trac #11465.  The check_unlifted check really isn't
necessary, as discussed in Trac #11120 comment:19.

Removing it made just one test-suite change,
in indexed-types/should_fail/T9357, by allowing

   type family F (a :: k1) :: k2
   type instance F Int# = Int

to be accepted.  And indeed that seems entirely reasonable.