The forced update should be the same as the OTA. It's hard to tell the source of the one you linked. However, some of the forced update files have the link directly to Google's servers, so you can be sure it is legit.
Here is the official link:
http://android.clients.google.com/updates/voles/signed-voles-FRG01B-from-ESE81.e48e48ff.zip