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_group.py

@@ -29,13 +29,9 @@ options:
    description:
      description:
         - Group description
-     required: false
-     default: None
    domain_id:
      description:
         - Domain id to create the group in if the cloud supports domains.
-     required: false
-     default: None
      version_added: "2.3"
    state:
      description:
@@ -45,7 +41,6 @@ options:
    availability_zone:
      description:
        - Ignored. Present for backwards compatibility
-     required: false
 requirements:
     - "python >= 2.6"
     - "shade"