Reduce logging noise in traceback output

When running tests locally Pytest returns a lot of captured logging info.

This is redundant because Pytest also captures stdout.

This commit effectively disables logging output when running tests by
setting the log level to higher than anything a real logging call would
ever emit.

The logging output is still captured by stdout, so nothing is lost here,
we’re just reducing duplication.

pytest.ini

@@ -1,5 +1,6 @@
 [pytest]
 testpaths = tests
+log_level = 999
 env =
     NOTIFY_ENVIRONMENT=test
     ADMIN_CLIENT_SECRET=dev-notify-secret-key