**Apache Airflow version**: 2.0.0b* / master


**What happened**:

`[ldap]` section in `airflow.cfg` is not applicable anymore in 2.0 and `master`, because the LDAP authentication (for webserver and API) is handled by FAB, and the configuration for this is handled by `webserver_config.py` file.

![airflow_–_default_airflow_cfg](https://user-images.githubusercontent.com/11539188/99289209-ef210700-283c-11eb-948e-16811ba09293.png)


**What you expected to happen**:

The `[ldap]` section should be removed from `airflow/config_templates/default_airflow.cfg` and `airflow/config_templates/config.yml` (and some other applicable files).

Otherwise leaving this section there will be a big confusion for users.
airflow/configuration.py
"""Historical load_test_config"""
    warnings.warn(
        "Accessing configuration method 'load_test_config' directly from the configuration module is "
        "deprecated. Please access the configuration from the 'configuration.conf' object via "
        "'conf.load_test_config'",
        DeprecationWarning,
        stacklevel=2,
    )
    conf.load_test_config()
def get(*args, **kwargs):  
    """Historical get"""
    warnings.warn(
        "Accessing configuration method 'get' directly from the configuration module is "
        "deprecated. Please access the configuration from the 'configuration.conf' object via "
        "'conf.get'",
        DeprecationWarning,
        stacklevel=2,
    )
    return conf.get(*args, **kwargs)
def getboolean(*args, **kwargs):