I had same problem, it was happened with me 2nd time today also when I updated Z10 OS. But what I did, I just turned off Facebook Notifications from Settings and then turned it on. All the old gone.
On the home screen of your BlackBerry device, swipe down from the top of the screen.
Tap Settings > Accounts > Facebook.
To turn off all Facebook notifications, set the Enable Notifications switch to Off.
To stop receiving Facebook messages in the BlackBerry Hub, set the Sync Messages switch to Off.
I had the same problem for last several FB updates, so much so that I grew hesitant to accept new updates. It has obviously to do with the new version syncing with FB after successful update and getting all the old notifications. At first it was very tiring as I new no shortcuts and would have to delete all of them one by one, which took for ever, now I simply use the 'delete prior" from the last entry and don't even think about it. But yeah, it would be nice if someone sorted it out either on FB side or BB10 side.