### 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)

airflow/providers/mongo/sensors/mongo.py
"""
    Checks for the existence of a document which
    matches the given query in MongoDB. Example:
    >>> mongo_sensor = MongoSensor(collection="coll",
    ...                            query={"key": "value"},
    ...                            mongo_conn_id="mongo_default",
    ...                            task_id="mongo_sensor")
    :param collection: Target MongoDB collection.
    :type collection: str
    :param query: The query to find the target document.
    :type query: dict
    :param mongo_conn_id: The :ref:`Mongo connection id <howto/connection:mongo>` to use
        when connecting to MongoDB.
    :type mongo_conn_id: str
    """
    template_fields = ('collection', 'query')
    def __init__(
        self, *, collection: str, query: dict, mongo_conn_id: str = "mongo_default", **kwargs
    ) -> None:
        super().__init__(**kwargs)
        self.mongo_conn_id = mongo_conn_id
        self.collection = collection
        self.query = query
    def poke(self, context: dict) -> bool:
        self.log.info(
            "Sensor check existence of the document that matches the following query: %s", self.query
        )
        hook = MongoHook(self.mongo_conn_id)
        return hook.find(self.collection, self.query, find_one=True) is not None