[LoopDeletion] Remove over-eager SCEV verification.

60b85209 introduced SCEV verification to
deleteDeadLoop, but it appears this check is currently a bit over-eager
and some users of deleteDeadLoop appear to only patch up SE after
calling it (e.g. PR47753).

Remove the extra check for now. We can consider adding it back after we
tracked down the source of the inconsistency for PR47753.