fix rules documentation for Notes (#1962)

Author: deniak

lib/rules.json

@@ -601,7 +601,6 @@
                             ],
                             "customParagraph": true,
                             "stability": "It <span class=\"rfc2119\">must</span> set expectations about the (in)stability of the document. The <span class=\"rfc2119\">recommended</span> text is: <blockquote class=\"boilerplate\"> <p>Group Notes are not endorsed by W3C nor its Members.</p> </blockquote> or <blockquote class=\"boilerplate\"> <p>This Group Note is endorsed by the @@@ Working/Interest Group (and the @@@ Working/Interest Group), but is not endorsed by W3C itself nor its Members.</p> </blockquote>",
-                            "draftStability": true,
                             "knownDisclosureNumber": true,
                             "patPolReq": true,
                             "whichProcess": true