Drop importlib.resources backport

[mattwthompson]

PR Summary:

This is in the standard library as of Python 3.10, so the third-party backport is not needed

PR Checklist

---

• Includes appropriate unit test(s)
• Appropriate docstring(s) are added/updated
• Code is (approximately) PEP8 compliant
• Issue(s) raised/addressed?

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.89%. Comparing base (b27e5c3) to head (5b78d29).
Report is 19 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1246   +/-   ##
=======================================
  Coverage   85.89%   85.89%           
=======================================
  Files          53       53           
  Lines        4862     4862           
=======================================
  Hits         4176     4176           
  Misses        686      686           

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