Revert "[lldb] Set default object format to `MachO` in `ObjectFileMachO` (#142704)"
This reverts commit d4d2f069dec4fb8b13447f52752d4ecd08d976d6.
Temporarily reverting until we can find a way to get the correct
ObjectFile set in Module's Triples without adding "-macho" to the
triple string for each Module. This is breaking TestUniversal.py
on the x86_64 macOS CI bots.