Remove pkg_resources import (deprecated module)

[furechan]

Summary of Changes

• pkg_resources is deprecated and causing import warnings in recent python versions
• pkg_resources was used only to fetch the package version as VERSION
• The version can be fetched directly from the __version__ submodule
• There is no need for pkg_resources or importlib.metadata

Checklist

• Code follows the style guidelines of this project
• Added tests for new functionality
• Update HISTORY.rst with an entry summarizing your change
• Tag a project maintainer