mathlib

ff8c8f58 - fix(tactic/norm_num): perform cleanup even if norm_num fails (#6655)

fix(tactic/norm_num): perform cleanup even if norm_num fails (#6655) [As reported on Zulip](https://leanprover.zulipchat.com/#narrow/stream/113488-general/topic/norm_num.20fails.20when.20simp.20is.20too.20effective/near/230004826). Co-authored-by: Scott Morrison <scott.morrison@gmail.com>