Replace deprecated datetime.utcfromtimestamp

[pavoljuhas]

Address DeprecationWarning about datetime.utcfromtimestamp.

Also suppress pytest warning about using pytest.raises with an empty
match pattern. Use None to skip checking exception message instead.

Reference: https://docs.python.org/3.12/library/datetime.html#datetime.datetime.utcfromtimestamp

[pavoljuhas]

NTS - hold until after #7677

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.37%. Comparing base (efb296e) to head (b7e933e).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7676      +/-   ##
==========================================
- Coverage   99.37%   99.37%   -0.01%     
==========================================
  Files        1084     1084              
  Lines       96917    96917              
==========================================
- Hits        96315    96314       -1     
- Misses        602      603       +1     

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