chore(doc-gen/angular.io): check for not private rather is public

In 2e4a2a0 we removed the `@public` tags but the `addJadeDataDocsProcessor`
was still relying upon them being there to identify whether a doc should
be included in the public docs.

Instead we should just check for the doc not being marked with the
`@private` tag.

Closes angular#3212

Author: petebacondarwin

docs/angular.io-package/processors/addJadeDataDocsProcessor.js

@@ -35,7 +35,7 @@ module.exports = function addJadeDataDocsProcessor() {
       */
 
       _.forEach(docs, function(doc) {
-        if (doc.docType === 'module' && doc.public && doc.exports.length) {
+        if (doc.docType === 'module' && !doc.private && doc.exports.length) {
           modules.push(doc);
 
           // GET DATA FOR INDEX PAGE OF MODULE SECTION