Replacing Function.prototype.bind with anonymous function

because Internet Explorer 8 does not know about .bind() and throws an
error. Consequently no "next" button is shown in the Upload Wizard User
Interface; thus IE 8 users were unable to upload files using Upload
Wizard before this patch was applied.

This regression was introduced in I5f35a701 (325b5ce2):
<https://git.wikimedia.org/blob/mediawiki%2Fextensions%2FUploadWizard/325b5ce20e82d00594480f10f749379c3549a65e/resources%2Fmw.UploadWizard.js#L720>.

Bug: 54392
Change-Id: I9d4509d37a8be094db2786562bc7773ba8b84141
Merge "Replacing Function.prototype.bind with anonymous function"