graphics/py-pillow: Update to 6.0.0

• Introduce a new option OLE and add it to the default options to maintain compatibility for a while with existing installations/users that rely on the previously deprecated function PIL.OleFileIO which has been removed now.
• Remove obsolete CONFLICTS_INSTALL entry because graphics/py-imaging no longer exists in the Ports tree since 2016.

Release Notes:

• https://pillow.readthedocs.io/en/latest/releasenotes/index.html

Backward Incompatible Changes (6.0.0):

• https://pillow.readthedocs.io/en/latest/releasenotes/6.0.0.html#backwards-incompatible-changes

Detailed Changelog:

• https://github.com/python-pillow/Pillow/blob/6.0.0/CHANGES.rst

PR: 237426
Reviewed by: antoine, koobs, Charlie Li
Approved by: koobs (maintainer)