Replace depricated datetime.datetime.utcnow() for datetime.datetime.n…

[cfernhout]

…ow(datetime.timezone.utc)

resolves #238 and #99

Description

Without this fix you have the stdout spam for Python 3.12 and up. datetime.UTC is an alias for datetime.timezone.utc.

/usr/local/lib/python3.12/site-packages/dbt_common/events/logger.py:159: DeprecationWarning: datetime.datetime.utcnow() is deprecated and scheduled for removal in a future version. Use timezone-aware objects to represent datetimes in UTC: datetime.datetime.now(datetime.UTC).
20:35:10  Completed successfully
/usr/local/lib/python3.12/site-packages/dbt_common/events/helpers.py:12: DeprecationWarning: datetime.datetime.utcnow() is deprecated and scheduled for removal in a future version. Use timezone-aware objects to represent datetimes in UTC: datetime.datetime.now(datetime.UTC).
/usr/local/lib/python3.12/site-packages/dbt_common/events/logger.py:159: DeprecationWarning: datetime.datetime.utcnow() is deprecated and scheduled for removal in a future version. Use timezone-aware objects to represent datetimes in UTC: datetime.datetime.now(datetime.UTC).
20:35:10  
/usr/local/lib/python3.12/site-packages/dbt_common/events/helpers.py:12: DeprecationWarning: datetime.datetime.utcnow() is deprecated and scheduled for removal in a future version. Use timezone-aware objects to represent datetimes in UTC: datetime.datetime.now(datetime.UTC).
/usr/local/lib/python3.12/site-packages/dbt_common/events/logger.py:159: DeprecationWarning: datetime.datetime.utcnow() is deprecated and scheduled for removal in a future version. Use timezone-aware objects to represent datetimes in UTC: datetime.datetime.now(datetime.UTC).
20:35:10  Done. PASS=10 WARN=0 ERROR=0 SKIP=0 TOTAL=10
/usr/local/lib/python3.12/site-packages/dbt_common/events/helpers.py:12: DeprecationWarning: datetime.datetime.utcnow() is deprecated and scheduled for removal in a future version. Use timezone-aware objects to represent datetimes in UTC: datetime.datetime.now(datetime.UTC).
/usr/local/lib/python3.12/site-packages/dbt_common/events/logger.py:159: DeprecationWarning: datetime.datetime.utcnow() is deprecated and scheduled for removal in a future version. Use timezone-aware objects to represent datetimes in UTC: datetime.datetime.now(datetime.UTC).

Checklist

• I have read the contributing guide and understand what's expected of me
• I have signed the CLA
• I have run this code in development and it appears to resolve the stated issue
• I have opened an issue to add/update docs, or docs changes are not required/relevant for this PR
• I have run changie new to create a changelog entry