[lld/mac] Don't warn on -bundle and -execute flags

They've been implemented since D87856 but since they still were
HelpHidden, the driver still warned claiming they were implemented.
Remove HelpHidden.

Use -fatal_warnings to test that the flags now don't warn. The
test depends on D91894 and D91891 to pass.

Differential Revision: https://reviews.llvm.org/D91971