Update timezone comparison in test_nc_tools

[douglatornell]

Changed dateutil.tz.tzutc() to datetime.timezone.utc in the timezone comparison assertion in test_nc_tools.py. This ensures compatibility with Python's standard library and resolves a failing test due to mismatched timezone objects.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 47.16%. Comparing base (02db019) to head (411615d).
⚠️ Report is 34 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #195   +/-   ##
=======================================
  Coverage   47.16%   47.16%           
=======================================
  Files          35       35           
  Lines        5025     5025           
=======================================
  Hits         2370     2370           
  Misses       2655     2655           

Flag	Coverage Δ
unittests	47.16% <100.00%> (ø)

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