Clean up module documentation (#36909)

* Clean up module documentation

This PR includes:
- Removal of `default: None` (and variations)
- Removal of `required: false`
- Fixing booleans and `type: bool` where required

* Fix remaining (new) validation issues

lib/ansible/modules/cloud/openstack/os_user_facts.py

@@ -31,18 +31,13 @@ options:
    domain:
      description:
         - Name or ID of the domain containing the user if the cloud supports domains
-     required: false
-     default: None
    filters:
      description:
         - A dictionary of meta data to use for further filtering.  Elements of
           this dictionary may be additional dictionaries.
-     required: false
-     default: None
    availability_zone:
      description:
        - Ignored. Present for backwards compatibility
-     required: false
 '''
 
 EXAMPLES = '''