Remove above divider of main switch

Problem: The main switch won't be the ceiling preference. It has chance to show the divider if another preference won't disable the below divider.
Solution: Remove the above divider.

Bug: 186066199
Test: Test: Manual testing
Change-Id: I49893fa71b016f82dce9f402d47c86ec3df20a54

src/com/android/settings/widget/SettingsMainSwitchPreference.java

@@ -74,7 +74,7 @@ public class SettingsMainSwitchPreference extends TwoStatePreference {
     public void onBindViewHolder(PreferenceViewHolder holder) {
         super.onBindViewHolder(holder);
 
-        holder.setDividerAllowedAbove(true);
+        holder.setDividerAllowedAbove(false);
         holder.setDividerAllowedBelow(false);
 
         mMainSwitchBar = (SettingsMainSwitchBar) holder.findViewById(R.id.main_switch_bar);