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/utilities/logic/set_fact.py

@@ -1,7 +1,7 @@
 #!/usr/bin/python
 # -*- coding: utf-8 -*-
 
-# Copyright 2013 Dag Wieers <dag@wieers.com>
+# Copyright: (c) 2013, Dag Wieers (@dagwieers) <dag@wieers.com>
 # GNU General Public License v3.0+ (see COPYING or https://www.gnu.org/licenses/gpl-3.0.txt)
 
 from __future__ import absolute_import, division, print_function
@@ -15,7 +15,8 @@ ANSIBLE_METADATA = {'metadata_version': '1.1',
 
 DOCUMENTATION = '''
 ---
-author: "Dag Wieers (@dagwieers)"
+author:
+- Dag Wieers (@dagwieers)
 module: set_fact
 short_description: Set host facts from a task
 description:
@@ -32,13 +33,12 @@ options:
         in the playbook scope. Or alternatively, accepts complex arguments
         using the C(args:) statement.
     required: true
-    default: null
   cacheable:
     description:
       - This boolean indicates if the facts set will also be added to the
         fact cache, if fact caching is enabled.
-    required: false
-    default: false
+    type: bool
+    default: 'no'
     version_added: "2.4"
 version_added: "1.2"
 notes: