Fix boolean choices in module docs fragments

A few of the docs fragments have the available choices for some params
defined as "BOOLEANS". Because choices accepts a list, it treats
"BOOLEANS" as an iterable and then generates a list composed of each
letter.

Instead, define the available choices as a list of `['yes', 'no']`,
as is common in most other modules.

lib/ansible/utils/module_docs_fragments/nxos.py

@@ -63,8 +63,8 @@ options:
         I(transport) argument is configured as nxapi.  If the transport
         argument is not nxapi, this value is ignored
     required: false
-    default: false
-    choices: BOOLEANS
+    default: no
+    choices: ['yes', 'no']
   provider:
     description:
       - Convience method that allows all M(nxos) arguments to be passed as