isAvailable is true by default in dev options

- isAvailable() is defaulted to return true for all developer options
 preferences
 - child controllers should override for custom hiding logic

Bug: 34203528
Test: make RunSettingsRoboTests -j40
Change-Id: I89921f801c25e74bf78d02c55b5f34cf1d464cd0

src/com/android/settings/development/BluetoothAbsoluteVolumePreferenceController.java

@@ -38,11 +38,6 @@ public class BluetoothAbsoluteVolumePreferenceController extends
         super(context);
     }
 
-    @Override
-    public boolean isAvailable() {
-        return true;
-    }
-
     @Override
     public String getPreferenceKey() {
         return BLUETOOTH_DISABLE_ABSOLUTE_VOLUME_KEY;