fixed minor issues with openstack docs not being valid yaml

lib/ansible/utils/module_docs_fragments/openstack.py

@@ -91,8 +91,7 @@ options:
     choices: [public, internal, admin]
     required: false
     default: public
-requirements:
-  - shade
+requirements: [shade]
 notes:
   - The standard OpenStack environment variables, such as C(OS_USERNAME)
     may be user instead of providing explicit values.