Fix count input on form collection

Author: matthieumota

form/form_collections.rst

@@ -328,7 +328,7 @@ will be show next):
 
         // count the current form inputs we have (e.g. 2), use that as the new
         // index when inserting a new item (e.g. 2)
-        $collectionHolder.data('index', $collectionHolder.find(':input').length);
+        $collectionHolder.data('index', $collectionHolder.find('input').length);
 
         $addTagButton.on('click', function(e) {
             // add a new tag form (see next code block)