[llvm-objcopy][MachO] Avoid accidental invalid relocations in tests

Until recently yaml2obj didn't properly support relocations for MachO.
This behavior resulted in binaries having invalid relocations.
In this diff we adjust the existing tests as follows:
for the tests which don't actually look at any relocations they are removed,
for the tests which essentially depend on relocations they are fixed.

Test plan: make check-all

Differential revision: https://reviews.llvm.org/D78898