Fix FastScroller jumping in recyclerView

FastScrolling is jumping crazily when VerticalSnapPreference is set SNAP_TO_START, rather SNAP_TO_ANY may be better.

bug:321835976
Test manual video:
before: https://drive.google.com/file/d/1OOWESXjclndNgDklPq1BXR5HDehqJuPe/view?usp=sharing
after: https://drive.google.com/file/d/1O6wRx4H9R-Di-lPTOY7SwrsxrBPhXHo-/view?usp=sharing
Flag: n/a

Change-Id: I6974c842aa88f6bc7df1011c05eecfde7dad766c

src/com/android/launcher3/allapps/AllAppsFastScrollHelper.java

@@ -71,7 +71,7 @@ public class AllAppsFastScrollHelper {
 
         @Override
         protected int getVerticalSnapPreference() {
-            return SNAP_TO_START;
+            return SNAP_TO_ANY;
         }
 
         @Override