Bug 1702978 - Reduce maximum allowed velocity when initiating overscroll snapback animation. r=botond

This makes it so that quick flings don't create such a large initial overscroll gap.

Before: https://share.firefox.dev/3fFP5Kp
After: https://share.firefox.dev/3fHA4b1

The "before" profile shows a jump from -65 to -320 in the overscroll amount, when
the animation is started, and the "after" profile shows a jump from -57 to -201.

Depends on D110844

Differential Revision: https://phabricator.services.mozilla.com/D110845

modules/libpref/init/StaticPrefList.yaml

@@ -608,7 +608,7 @@
 
 - name: apz.overscroll.max_velocity
   type: AtomicFloat
-  value: 20
+  value: 10
   mirror: always
 
 - name: apz.paint_skipping.enabled