Makefile.PL: Change path to enums.pod in build; fixes RT#89188

- Newer versions of ExtUtils::MakeMaker sort files listed in MAN3PODЅ
  differently in newer versions than older versions, causing
  'enums.pod' to be generated before it's target directory has been
  created in the output 'blib' directory
- Back out the addition of 'mkdir' made in #0f30b57