'Mobile plan' is searchable even if it is unavailable

'Mobile plan' yields a search hit event though the 'Mobile plan'
setting is unavailable on the device.

Bug: 287198186
Test: Manual
Change-Id: Ibc6f01602a364ae902f8a6ce15083890e89446d2

src/com/android/settings/network/NetworkDashboardFragment.java

@@ -174,5 +174,17 @@ public class NetworkDashboardFragment extends DashboardFragment implements
                             null /* metricsFeatureProvider */, null /* fragment */,
                             null /* mobilePlanHost */);
                 }
+
+                @Override
+                public List<String> getNonIndexableKeys(Context context) {
+                    final List<String> keys = super.getNonIndexableKeys(context);
+
+                    MobilePlanPreferenceController mppc =
+                            new MobilePlanPreferenceController(context, null);
+                    if (!mppc.isAvailable()) {
+                        keys.add(MobilePlanPreferenceController.KEY_MANAGE_MOBILE_PLAN);
+                    }
+                    return keys;
+                }
             };
 }