Clean up unused NetworkPolicyEditor

From DataUsageSummaryPreferenceController.

NetworkPolicyEditor.read() is not called, so
NetworkPolicyEditor.getPolicy() will always returns null.

Data limit info is already set in getDataUsageInfo().

Bug: 295260929
Test: robo test
Change-Id: I56a40cc906aa95207785886e704b1a59ea344e9c

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

@@ -55,7 +55,6 @@ public class WifiDataUsageSummaryPreferenceController extends DataUsageSummaryPr
         }
         final DataUsageController.DataUsageInfo info = mDataUsageController.getDataUsageInfo(
                 template);
-        mDataInfoController.updateDataLimit(info, mPolicyEditor.getPolicy(template));
 
         mPreference.setWifiMode(/* isWifiMode */ true, /* usagePeriod */
                 info.period, /* isSingleWifi */ true);