**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
super().read(filenames=filenames, encoding=encoding)
        self._validate()
    def read_dict(self, dictionary, source='<dict>'):
        super().read_dict(dictionary=dictionary, source=source)
        self._validate()
    def has_option(self, section, option):
        try:
            
            
            
            self.get(section, option, fallback=_UNSET)
            return True
        except (NoOptionError, NoSectionError):
            return False
    def remove_option(self, section, option, remove_default=True):