Remove advertising show_diff feature

--diff will be added to more modules soon, and we want puppet module to utilize this instead of show_diff

lib/ansible/modules/extras/system/puppet.py

@@ -47,12 +47,6 @@ options:
       - Path to the manifest file to run puppet apply on.
     required: false
     default: None
-  show_diff:
-    description:
-      - Should puppet return diffs of changes applied. Defaults to off to avoid leaking secret changes by default.
-    required: false
-    default: no
-    choices: [ "yes", "no" ]
   facts:
     description:
       - A dict of values to pass in as persistent external facter facts
@@ -113,7 +107,7 @@ def main():
             puppetmaster=dict(required=False, default=None),
             manifest=dict(required=False, default=None),
             show_diff=dict(
-                default=False, aliases=['show-diff'], type='bool'),
+                default=False, aliases=['show-diff'], type='bool'), # internal code to work with --diff, do not use
             facts=dict(default=None),
             facter_basename=dict(default='ansible'),
             environment=dict(required=False, default=None),