Remove test_deserialization_across_process from quarantine (#15264)

I have not seen `TestStringifiedDAGs.test_deserialization_across_process` failing from a long time.

Based on apache/airflow#10118 -- this is the only test we should un-quarantine for now as I have seen the other tests failing here and there

GitOrigin-RevId: 076eaeaa2bec38960fb4d9a24c28c03321e9a00c

tests/serialization/test_dag_serialization.py

@@ -303,7 +303,6 @@ def sorted_serialized_dag(dag_dict: dict):
 
         assert sorted_serialized_dag(ground_truth_dag) == sorted_serialized_dag(json_dag)
 
-    @pytest.mark.quarantined
     def test_deserialization_across_process(self):
         """A serialized DAG can be deserialized in another process."""