Reproduce asyncio failure with stackdriver leaking pytest fixture tasks

There is a very strange error in our test suite which only occurs in
Postgres + Python 3.10 combination of tests where apparently a
non-cancelled test from pytest-asyncio fixtured event loop is cancelled
much later in different tests, producing an unexpected log entry and
failing TestGetGcpCredentialsAndProjectId.test_disable_logging.

See apache#36440 and likely the
root cause is pytest-dev/pytest-asyncio#200

This PR will allow to test the hypothesis and might help to iterate
over potential solutions.

airflow/providers/google/cloud/log/stackdriver_task_handler.py

@@ -30,21 +30,13 @@
 
 from airflow.providers.google.cloud.utils.credentials_provider import get_credentials_and_project_id
 from airflow.providers.google.common.consts import CLIENT_INFO
+from airflow.utils.log.trigger_handler import ctx_indiv_trigger
 
 if TYPE_CHECKING:
-    from contextvars import ContextVar
-
     from google.auth.credentials import Credentials
 
     from airflow.models import TaskInstance
 
-try:
-    # todo: remove this conditional import when min airflow version >= 2.6
-    ctx_indiv_trigger: ContextVar | None
-    from airflow.utils.log.trigger_handler import ctx_indiv_trigger
-except ImportError:
-    ctx_indiv_trigger = None
-
 DEFAULT_LOGGER_NAME = "airflow"
 _GLOBAL_RESOURCE = Resource(type="global", labels={})