Mark two tests as (trigger and deps) as flaky (#40144)

Those two tests are failing sometimes when run in parallel setting.
Not very frequently but frequently enough to be annoying, Seems that
they are really re-runnable and apparently there are some racy
behaviours triggering it, so marking them as flaky should help.

tests/ti_deps/deps/test_trigger_rule_dep.py

@@ -1135,6 +1135,7 @@ def test_mapped_task_upstream_removed_with_all_failed_trigger_rules(
 
         _test_trigger_rule(ti=ti, session=session, flag_upstream_failed=flag_upstream_failed)
 
+    @pytest.mark.flaky(reruns=5)
     @pytest.mark.parametrize(
         "trigger_rule", [TriggerRule.NONE_FAILED, TriggerRule.NONE_FAILED_MIN_ONE_SUCCESS]
     )

tests/triggers/test_external_task.py

@@ -74,6 +74,7 @@ async def test_task_workflow_trigger_success(self, mock_get_count):
         with pytest.raises(StopAsyncIteration):
             await gen.__anext__()
 
+    @pytest.mark.flaky(reruns=5)
     @mock.patch("airflow.triggers.external_task._get_count")
     @pytest.mark.asyncio
     async def test_task_workflow_trigger_failed(self, mock_get_count):