**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
('celery', 'flower_basic_auth'),
        ('celery', 'result_backend'),
        ('atlas', 'password'),
        ('smtp', 'smtp_password'),
        ('ldap', 'bind_password'),
        ('kubernetes', 'git_password'),
    }
    
    
    
    deprecated_options = {
        ('logging', 'base_log_folder'): ('core', 'base_log_folder'),
        ('logging', 'remote_logging'): ('core', 'remote_logging'),
        ('logging', 'remote_log_conn_id'): ('core', 'remote_log_conn_id'),
        ('logging', 'remote_base_log_folder'): ('core', 'remote_base_log_folder'),
        ('logging', 'encrypt_s3_logs'): ('core', 'encrypt_s3_logs'),
        ('logging', 'logging_level'): ('core', 'logging_level'),
        ('logging', 'fab_logging_level'): ('core', 'fab_logging_level'),
        ('logging', 'logging_config_class'): ('core', 'logging_config_class'),
        ('logging', 'colored_console_log'): ('core', 'colored_console_log'),
        ('logging', 'colored_log_format'): ('core', 'colored_log_format'),
        ('logging', 'colored_formatter_class'): ('core', 'colored_formatter_class'),
        ('logging', 'log_format'): ('core', 'log_format'),
        ('logging', 'simple_log_format'): ('core', 'simple_log_format'),
        ('logging', 'task_log_prefix_template'): ('core', 'task_log_prefix_template'),
        ('logging', 'log_filename_template'): ('core', 'log_filename_template'),
        ('logging', 'log_processor_filename_template'): ('core', 'log_processor_filename_template'),
        ('logging', 'dag_processor_manager_log_location'): ('core', 'dag_processor_manager_log_location'),
        ('logging', 'task_log_reader'): ('core', 'task_log_reader'),
        ('metrics', 'statsd_on'): ('scheduler', 'statsd_on'),