Unaccelerated deltas make sure the gesture works the same regardless of how fast the fingers move; this is what we were already doing for scrolling.
Remove the swipe multiplier as the deltas already match scrolling other than the 1/10 multiplier Clutter applies to scrolling specifically.
Split from !1731 (merged), includes it as well.
This requires new API in libinput and porting Mutter to use it, see: