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/database/misc/riak.py

@@ -28,47 +28,35 @@ options:
   command:
     description:
       - The command you would like to perform against the cluster.
-    required: false
-    default: null
     choices: ['ping', 'kv_test', 'join', 'plan', 'commit']
   config_dir:
     description:
       - The path to the riak configuration directory
-    required: false
     default: /etc/riak
   http_conn:
     description:
       - The ip address and port that is listening for Riak HTTP queries
-    required: false
     default: 127.0.0.1:8098
   target_node:
     description:
       - The target node for certain operations (join, ping)
-    required: false
     default: riak@127.0.0.1
   wait_for_handoffs:
     description:
       - Number of seconds to wait for handoffs to complete.
-    required: false
-    default: null
   wait_for_ring:
     description:
       - Number of seconds to wait for all nodes to agree on the ring.
-    required: false
-    default: null
   wait_for_service:
     description:
       - Waits for a riak service to come online before continuing.
-    required: false
-    default: None
     choices: ['kv']
   validate_certs:
     description:
       - If C(no), SSL certificates will not be validated. This should only be used
         on personally controlled sites using self-signed certificates.
-    required: false
+    type: bool
     default: 'yes'
-    choices: ['yes', 'no']
     version_added: 1.5.1
 '''