Build: Update download.jqueryui.com from 2.2.5 to 2.2.6

This resolves the issue of `download.jqueryui.com`'s `prepare-jquery-ui` task
requiring a global `grunt` binary.

Author: mgol

package-lock.json

@@ -21,7 +21,7 @@
   ],
   "dependencies": {
     "cheerio": "0.22.0",
-    "download.jqueryui.com": "2.2.5",
+    "download.jqueryui.com": "2.2.6",
     "grunt": "1.4.0",
     "grunt-cli": "1.4.2",
     "grunt-jquery-content": "3.1.0"