### Description

[MongoSensor](https://airflow.apache.org/docs/apache-airflow-providers-mongo/2.1.0/_api/airflow/providers/mongo/sensors/mongo/index.html) does not have a DB in the Python API. It has to use the schema from Mongo Connection. 



### Use case/motivation

In mongo, the schema is usually the Auth DB and not the data DB. The user will not have the option to switch DB at the DAG level.

### Related issues

_No response_

### Are you willing to submit a PR?

- [X] Yes I am willing to submit a PR!

### Code of Conduct

- [X] I agree to follow this project's [Code of Conduct](https://github.com/apache/airflow/blob/main/CODE_OF_CONDUCT.md)

tests/providers/mongo/sensors/test_mongo.py
def setUp(self):
        db.merge_conn(
            Connection(conn_id='mongo_test', conn_type='mongo', host='mongo', port='27017', schema='test')
        )
        args = {'owner': 'airflow', 'start_date': DEFAULT_DATE}
        self.dag = DAG('test_dag_id', default_args=args)
        hook = MongoHook('mongo_test')
        hook.insert_one('foo', {'bar': 'baz'})
        self.sensor = MongoSensor(
            task_id='test_task',
            mongo_conn_id='mongo_test',
            dag=self.dag,
            collection='foo',
            query={'bar': 'baz'},
        )
    def test_poke(self):
        assert self.sensor.poke(None)