Bug 42070: Hide "Use smooth scrolling" from settings

browser/components/preferences/main.inc.xhtml

@@ -724,7 +724,8 @@
             preference="general.autoScroll"/>
   <checkbox id="useSmoothScrolling"
             data-l10n-id="browsing-use-smooth-scrolling"
-            preference="general.smoothScroll"/>
+            preference="general.smoothScroll"
+            hidden="true"/>
 #ifdef MOZ_WIDGET_GTK
   <checkbox id="useOverlayScrollbars"
             data-l10n-id="browsing-gtk-use-non-overlay-scrollbars"