ansible-local/ansible: Clearify docs regarding `extra_arguments`

Closes: #4822

website/source/docs/provisioners/ansible-local.html.md

@@ -53,7 +53,8 @@ Optional:
     To disable colors, set this to `PYTHONUNBUFFERED=1 ansible-playbook`.
 
 - `extra_arguments` (array of strings) - An array of extra arguments to pass
-    to the ansible command. By default, this is empty.
+    to the ansible command. By default, this is empty. These arguments _will_
+    be passed through a shell and arguments should be quoted accordingly.
     Usage example:
 
 ```

website/source/docs/provisioners/ansible.html.md

@@ -92,7 +92,8 @@ Optional Parameters:
   Defaults to false.
 
 - `extra_arguments` (array of strings) - Extra arguments to pass to Ansible.
-  Usage example:
+  These arguments _will not_ be passed through a shell and arguments should
+  not be quoted. Usage example:
 
     ```json
     {