[AArch64][MachO] Drop a 2015 ld64 workaround avoiding local relocations

Commit d6223a24 introduced an ld64 workaround
that disables local relocations for many pointer-sized relocations (e.g.
relocations referencing `__DATA,__literal*`).

ld64 has been fixed long ago (2015). Drop this workaround so that the
behavior matches x86-64.

Reviewed By: pete

Differential Revision: https://reviews.llvm.org/D152831