**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
self,
        display_source=False,
        display_sensitive=False,
        raw=False,
        include_env=True,
        include_cmds=True,
        include_secret=True,
    ) -> Dict[str, Dict[str, str]]:
        """
        Returns the current configuration as an OrderedDict of OrderedDicts.
        :param display_source: If False, the option value is returned. If True,
            a tuple of (option_value, source) is returned. Source is either
            'airflow.cfg', 'default', 'env var', or 'cmd'.
        :type display_source: bool
        :param display_sensitive: If True, the values of options set by env
            vars and bash commands will be displayed. If False, those options
            are shown as '< hidden >'
        :type display_sensitive: bool
        :param raw: Should the values be output as interpolated values, or the
            "raw" form that can be fed back in to ConfigParser
        :type raw: bool
        :param include_env: Should the value of configuration from AIRFLOW__
            environment variables be included or not