fix deprecation warnings for iter_entry_points

[hamarituc]

Invoking space with recent Python versions produces a deprecation warning.

$ space
/usr/lib/python3.13/site-packages/space/wspace.py:11: UserWarning: pkg_resources is deprecated as an API. See https://setuptools.pypa.io/en/latest/pkg_resources.html. The pkg_resources package is slated for removal as early as 2025-11-30. Refrain from using this package or pin to Setuptools<81.
  from pkg_resources import iter_entry_points

This PR removes the deprecated iter_entry_points-import.

Consider removing support for deprecated Python versions (3.9 and earlier). References to iter_entry_points can then be removed at all.