You can't clear it, but the updates will drop off after a week or so. They do this because of the new Auto Update Apps feature. You can have it update your apps automatically, so they have this list of updated apps so you can see what updated and what was changed.
Me too, just updated two apps an hour ago and they are still there under a heading "Updated September 19". Personally I think this might be nice to keep track of recently updated apps. The badge was not there.
They last maybe a week and then disappear. I don't think it such a big issue - how often do you go into the updated tab and at least it doesn't badge the icon or show them somewhere else (besides the NC where they can be dismissed).