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/source_control/github_issue.py

@@ -22,22 +22,18 @@ options:
     description:
       - Name of repository from which issue needs to be retrieved.
     required: true
-    default: none
   organization:
     description:
       - Name of the GitHub organization in which the repository is hosted.
     required: true
-    default: none
   issue:
     description:
       - Issue number for which information is required.
-    default: none
     required: true
   action:
     description:
         - Get various details about issue depending upon action specified.
     default: 'get_status'
-    required: false
     choices:
         - ['get_status']