Build: Update version from pre to -pre

Ref jquery/jquery-release#61
Fixes #15020
Closes gh-1561

package.json

@@ -2,7 +2,7 @@
   "name": "jquery",
   "title": "jQuery",
   "description": "JavaScript library for DOM operations",
-  "version": "2.1.1pre",
+  "version": "2.1.1-pre",
   "main": "dist/jquery.js",
   "homepage": "http://jquery.com",
   "author": {