**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
for (source_name, config) in configs:
            for section in config.sections():
                AirflowConfigParser._replace_section_config_with_display_sources(
                    config, config_sources, display_source, raw, section, source_name
                )
    @staticmethod
    def _replace_section_config_with_display_sources(
        config, config_sources, display_source, raw, section, source_name
    ):
        sect = config_sources.setdefault(section, OrderedDict())
        for (k, val) in config.items(section=section, raw=raw):
            if display_source:
                val = (val, source_name)
            sect[k] = val
    def load_test_config(self):
        """
        Load the unit test configuration.
        Note: this is not reversible.
        """
        
        log.info("Overriding settings with defaults from %s", DEFAULT_CONFIG_FILE_PATH)
        self.read_string(parameterized_config(DEFAULT_CONFIG))
        
        log.info("Reading default test configuration from %s", TEST_CONFIG_FILE_PATH)
        self.read_string(parameterized_config(TEST_CONFIG))
        
        log.info("Reading test configuration from %s", TEST_CONFIG_FILE)
        self.read(TEST_CONFIG_FILE)
    @staticmethod
    def _warn_deprecate(section, key, deprecated_section, deprecated_name):