fix email is sent when normal confirmation icon clicked

[``* `#17584 ` email is sent when normal confirmation icon clicked``](http://community.openproject.org/work_packages/17584)
@0xF013 we could take advantage of URI.js here. Then we don't need to fiddle around with String concatenation and coercion: 
```js
URI(workPackage.links.updateImmediately.href).addSearch('notify', notify).toString();
```