Replace usage of datetime.utcnow() with datetime.now(UTC)
This MR replaces all usage of datetime.datetime.utcnow() with datetime.datetime.now(datetime.UTC). The former is deprecated as of Python 3.12.
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This MR replaces all usage of datetime.datetime.utcnow() with datetime.datetime.now(datetime.UTC). The former is deprecated as of Python 3.12.