perf: Re-enable msd physics for smooth scrolling, b=no-bug, c=no-component

Author: mr-cheffy

src/browser/app/profile/smoothscroll.inc

@@ -2,6 +2,7 @@
 // License, v. 2.0. If a copy of the MPL was not distributed with this
 // file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
+pref("general.smoothScroll.msdPhysics.enabled", true);
 pref("general.smoothScroll.currentVelocityWeighting", "0.15");
 pref("general.smoothScroll.stopDecelerationWeighting", "0.6");
 pref("mousewheel.min_line_scroll_amount", 10);