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/smartos/smartos_image_facts.py

@@ -29,8 +29,6 @@ options:
               manifest and 'published_date', 'published', 'source', 'clones',
               and 'size'. More informaton can be found at U(https://smartos.org/man/1m/imgadm)
               under 'imgadm list'.
-        required: false
-        default: None
 '''
 
 EXAMPLES = '''