[lld-macho] Fix unwind info personality size

This was missed by {D107035}. This fix addresses the following warning:

  loop variable 'personality' has type 'const uint32_t &' (aka 'const unsigned int &') but is initialized with type 'const unsigned long long' resulting in a copy [-Wrange-loop-analysis]

In addition to fixing the size, I also removed the const reference,
since there's no performance benefit to avoiding copies of integer-sized
values.