Remove pkg_resources (deprecated)

[dgarcia360]

Motivation

Use of pkg_resources is deprecated in favor of importlib.resources, importlib.metadata and their backports (importlib_resources, importlib.metadata). Some useful APIs are also provided by packaging (e.g. requirements and version parsing). Users should refrain from new usage of pkg_resources and should work to port to importlib-based solutions.

From https://setuptools.pypa.io/en/latest/pkg_resources.html

Replaces pkg_resources for importlib.metadata

How to test

Docs should build without errors.

[annastuchlik]

I've build this PR locally without any errors.

[annastuchlik]

LGTM, thanks.