devel/meson: Revert "build for all Python versions (for graphics/blender)"

Reverted as requested due to lack of approval by the python team.
There's also a build problem in dependent ports due to
USE_PYTHON=concurrent which requires additional detail work to address.

PORTEPOCH bump as USE_PYTHON=concurrent changes the plist.

Reported by: antoine
Requested by: arrowd, mat
PR: 296086

This reverts commit d0e08ee74bc97443bce5d03d899b74ce266f64d5.