[ExpandReductions] fix FMF requirement for fmin/fmax

The upstream callers (the vectorizers) were fixed with:
bbed5f2f ( D95690 )
77adbe6a

We should remove this pass entirely now that reduction
legalization/lowering is expected to work just as well,
but we need to confirm that the shuffle ops do not
regress (for x86 in particular).

This should be the last step needed to close:
https://llvm.org/PR23116