don't use system tz, display timestamps as UTC

no particular reason, just one less dependency, and it goes further
towards my idyllic world where everyone is on UTC and there are no
timezones

requirements/requirements-dev.txt

@@ -116,8 +116,6 @@ pytest==7.1.1
     #   pytest-cov
 pytest-cov==3.0.0
     # via -r requirements/requirements-dev.in
-pytz-deprecation-shim==0.1.0.post0
-    # via tzlocal
 pyyaml==6.0
     # via
     #   bandit
@@ -154,10 +152,6 @@ tox==3.24.5
     #   tox-wheel
 tox-wheel==0.7.0
     # via -r requirements/requirements-dev.in
-tzdata==2022.1
-    # via pytz-deprecation-shim
-tzlocal==4.1
-    # via -r requirements/requirements.in
 urllib3==1.26.9
     # via requests
 versioneer==0.22