Replace deprecated `pkg_resources` with `importlib.metadata.version`

[janosh]

From https://setuptools.pypa.io:

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.

[codecov-commenter]

Codecov Report

All modified lines are covered by tests :white_check_mark:

Comparison is base (e4d3b75) 91.34% compared to head (e9a8ec5) 91.34%. Report is 1 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #862 +/- ## ======================================= Coverage 91.34% 91.34% ======================================= Files 138 138 Lines 12749 12749 ======================================= Hits 11646 11646 Misses 1103 1103 ``` | [Files](https://app.codecov.io/gh/materialsproject/emmet/pull/862?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=materialsproject) | Coverage Δ | | |---|---|---| | [emmet-core/emmet/core/\_\_init\_\_.py](https://app.codecov.io/gh/materialsproject/emmet/pull/862?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=materialsproject#diff-ZW1tZXQtY29yZS9lbW1ldC9jb3JlL19faW5pdF9fLnB5) | `100.00% <100.00%> (ø)` | |

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[munrojm]

Thanks!