The helm-chart should not force the settings of Resultsbackend, Metadata and Broker. Either through an additional configuration option or implicitly by not providing values, the helm-chart should refrain from populating those Airflow-Env configurations.

**Use case / motivation**
The current Helm chart forces the configuration of certain values such as `brokerUrl` (https://github.com/apache/airflow/blob/main/chart/values.yaml#L236)
Which will then be populated as Airflow ENV config.
Due to Airflows configuration precedence (https://airflow.apache.org/docs/apache-airflow/stable/howto/set-config.html) are these settings taking highest priority in Airflow configuration.

With the suggested change, users can dynamically provide Airflow configurations through Airflow's `__CMD` environment variables.

**In other words; provide users with the option to utilize Airflow's `__CMD` ENV configuration.**

_I am willing to submit a PR._

chart/tests/test_airflow_common.py
"""
        Test Annotations are correctly applied on all pods created Scheduler, Webserver & Worker
        deployments.
        """
        release_name = "TEST-BASIC"
        k8s_objects = render_chart(
            name=release_name,
            values={
                "airflowPodAnnotations": {"test-annotation/safe-to-evict": "true"},
            },
            show_only=[
                "templates/scheduler/scheduler-deployment.yaml",
                "templates/workers/worker-deployment.yaml",
                "templates/webserver/webserver-deployment.yaml",
                "templates/flower/flower-deployment.yaml",
                "templates/triggerer/triggerer-deployment.yaml",
            ],
        )
        assert 5 == len(k8s_objects)
        for k8s_object in k8s_objects:
            annotations = k8s_object["spec"]["template"]["metadata"]["annotations"]
            assert "test-annotation/safe-to-evict" in annotations
            assert "true" in annotations["test-annotation/safe-to-evict"]
    @pytest.mark.parametrize(
        "use_default_image,expected_image",
        [
            (True, "apache/airflow:2.1.0"),
            (False, "apache/airflow:user-image"),
        ],