Why? [`pre-uglify`](https://github.com/mzgol/jquery/blob/cbe0b428180a935abe447ca55213e1762b072492/Gruntfile.js#L526) is supposed to produce the input we *really* want for `uglify`—namely, a copy of `dist/jquery.js` with all banners removed and the new (small) banner, if any, added to the top.