Address some FIXMEs left over from #91475#91577

Merged

bors merged 2 commits intorust-lang:masterfrom ecstatic-morse:mir-pass-manager-cleanup

Dec 8, 2021

+15-16

Commits on Dec 5, 2021

Remove unnecessary FIXME (answered by Oli)
ecstatic-morse
committed

Commits on Dec 6, 2021

Make treatment of generator drop shims explicit
ecstatic-morse
committed