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/elasticache_parameter_group.py

@@ -38,7 +38,6 @@ options:
       - The name of the cache parameter group family that the cache parameter group can be used with.
         Required when creating a cache parameter group.
     choices: ['memcached1.4', 'redis2.6', 'redis2.8', 'redis3.2']
-    required: no
   name:
     description:
      - A user-specified name for the cache parameter group.
@@ -54,8 +53,6 @@ options:
   values:
     description:
       - A user-specified dictionary of parameters to reset or modify for the cache parameter group.
-    required: no
-    default: None
 """
 
 EXAMPLES = """