Clean up ChartDataUsagePreference.setColors()

This method is no-op.

Bug: 290856342
Test: manual - on DataUsageList
Change-Id: Ice64630bc43afe7116b797425a5ea81b2d0ad5af

src/com/android/settings/datausage/ChartDataUsagePreference.java

@@ -56,8 +56,6 @@ public class ChartDataUsagePreference extends Preference {
     private long mStart;
     private long mEnd;
     private NetworkCycleChartData mNetworkCycleChartData;
-    private int mSecondaryColor;
-    private int mSeriesColor;
 
     public ChartDataUsagePreference(Context context, AttributeSet attrs) {
         super(context, attrs);
@@ -310,10 +308,4 @@ public class ChartDataUsagePreference extends Preference {
         mEnd = data.getEndTime();
         notifyChanged();
     }
-
-    public void setColors(int seriesColor, int secondaryColor) {
-        mSeriesColor = seriesColor;
-        mSecondaryColor = secondaryColor;
-        notifyChanged();
-    }
 }