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
docs = render_chart(
            values={
                "dags": dag_values,
                "airflowVersion": "1.10.15",
            },  
            show_only=[
                "templates/scheduler/scheduler-deployment.yaml",
                "templates/workers/worker-deployment.yaml",
                "templates/webserver/webserver-deployment.yaml",
            ],
        )
        assert 3 == len(docs)
        for doc in docs:
            expected_mount = {
                "mountPath": "/opt/airflow/dags",
                "name": "dags",
                "readOnly": expected_read_only,
            }
            assert expected_mount in jmespath.search("spec.template.spec.containers[0].volumeMounts", doc)
    def test_annotations(self):