**Description**

Make HttpSensor `headers` parameter templated.

**Use case / motivation**

This would allow for passing data from other tasks, such as an API token, in the headers.

**Related Issues**

N/A
airflow/providers/http/sensors/http.py
# In practice you would do something more sensible with this data..
            print(xcom_data)
            return True
        HttpSensor(task_id='my_http_sensor', ..., response_check=response_check)
    .. seealso::
        For more information on how to use this operator, take a look at the guide:
        :ref:`howto/operator:HttpSensor`
    :param http_conn_id: The connection to run the sensor against
    :type http_conn_id: str
    :param method: The HTTP request method to use
    :type method: str
    :param endpoint: The relative part of the full url
    :type endpoint: str
    :param request_params: The parameters to be added to the GET url
    :type request_params: a dictionary of string key/value pairs
    :param headers: The HTTP headers to be added to the GET request
    :type headers: a dictionary of string key/value pairs
    :param response_check: A check against the 'requests' response object.
        The callable takes the response object as the first positional argument
        and optionally any number of keyword arguments available in the context dictionary.
        It should return True for 'pass' and False otherwise.
    :type response_check: A lambda or defined function.
    :param extra_options: Extra options for the 'requests' library, see the
        'requests' documentation (options to modify timeout, ssl, etc.)
    :type extra_options: A dictionary of options, where key is string and value
        depends on the option that's being modified.
    """
    template_fields = ('endpoint', 'request_params')
    @apply_defaults
    def __init__(