DeprecationWarning: `datetime.datetime.utcfromtimestamp()` is deprecated and scheduled for removal in a future version

[ianna]

Version of Awkward Array

2.6.5 (master branch)

Description and code to reproduce

/Users/runner/work/awkward/awkward/dev/generate-kernel-signatures.py:134: DeprecationWarning: datetime.datetime.utcfromtimestamp() is deprecated and scheduled for removal in a future version. Use timezone-aware objects to represent datetimes in UTC: datetime.datetime.fromtimestamp(timestamp, datetime.UTC).

/Users/runner/work/awkward/awkward/dev/generate-tests.py:22: DeprecationWarning: datetime.datetime.utcfromtimestamp() is deprecated and scheduled for removal in a future version. Use timezone-aware objects to represent datetimes in UTC: datetime.datetime.fromtimestamp(timestamp, datetime.UTC).
  build_date = datetime.datetime.utcfromtimestamp(