This removes the `defer_me` check that was in checkTauTvUpdate
and uses only a type family check instead. The old defer_me check
repeated work done by fast_check in occurCheckExpand.

There is also some error message improvement, necessitated by
the terrible error message that the test case produced, even when
it didn't consume all of memory.

test case: dependent/should_fail/T11407

[skip ci]