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/amazon/iam_policy.py

@@ -30,7 +30,6 @@ options:
     description:
       - Type of IAM resource
     required: true
-    default: null
     choices: [ "user", "group", "role"]
   iam_name:
     description:
@@ -43,23 +42,19 @@ options:
   policy_document:
     description:
       - The path to the properly json formatted policy file (mutually exclusive with C(policy_json))
-    required: false
   policy_json:
     description:
       - A properly json formatted policy as string (mutually exclusive with C(policy_document),
         see https://github.com/ansible/ansible/issues/7005#issuecomment-42894813 on how to use it properly)
-    required: false
   state:
     description:
       - Whether to create or delete the IAM policy.
     required: true
-    default: null
     choices: [ "present", "absent"]
   skip_duplicates:
     description:
       - By default the module looks for any policies that match the document you pass in, if there is a match it will not make a new policy object with
         the same rules. You can override this by specifying false which would allow for two policy objects with different names but same rules.
-    required: false
     default: "/"
 
 notes: