[AIRFLOW-4252] Remove the unused sessions (apache#5051)

* [AIRFLOW-4252] Remove the unused sessions

Some housekeeping

* [AIRFLOW-4252] Remove the provide_context

airflow/models/__init__.py

@@ -3408,12 +3408,10 @@ def handle_callback(self, dagrun, success=True, reason=None, session=None):
             context.update({'reason': reason})
             callback(context)
 
-    @provide_session
-    def get_active_runs(self, session=None):
+    def get_active_runs(self):
         """
         Returns a list of dag run execution dates currently running
 
-        :param session:
         :return: List of execution dates
         """
         runs = DagRun.find(dag_id=self.dag_id, state=State.RUNNING)
@@ -3840,8 +3838,7 @@ def get_task(self, task_id):
             return self.task_dict[task_id]
         raise AirflowException("Task {task_id} not found".format(task_id=task_id))
 
-    @provide_session
-    def pickle_info(self, session=None):
+    def pickle_info(self):
         d = dict()
         d['is_picklable'] = True
         try: