Fix -Wcovered-switch-default in MachOUniversalWriter.cpp (NFC)

/llvm-project/llvm/lib/Object/MachOUniversalWriter.cpp:351:3: error: default label in switch which covers all enumeration values [-Werror,-Wcovered-switch-default]
  default:
  ^
1 error generated.

GitOrigin-RevId: a5b45b48ece35f05ed53440bc792193db52b8b1b
1 file changed