PEP 376: Fix implementation details section to match reality

[ncoghlan]

The part of PEP 376 that was actually accepted is the installation directory layout - the discussion of Python level APIs in the "Implementation Details" section isn't accurate.

This section should be updated to point readers towards distlib and importlib-metadata instead.

[AA-Turner]

@ncoghlan is this issue still outstanding?

A

[CAM-Gerlach]

If this is still an issue, it can potentially be updated on the PyPUG specifications section instead

[ncoghlan]

Good catch, as this was addressed a couple of years ago: #1307

As @CAM-Gerlach noted, the actual reference docs are also now at https://packaging.python.org/en/latest/specifications/recording-installed-packages/ so folks are much less likely to be looking directly at PEP 376 in the first place.