Set phone number preference unselectable

For multiple sim case, there are two or more phone number preferences in
About page. They should be grayed out because they don't have actions.

Fixes: 138263122
Test: Visual
Change-Id: I86ec37d049983c23b8990dda0e12bfadebf70d1e

src/com/android/settings/deviceinfo/PhoneNumberPreferenceController.java

@@ -77,6 +77,7 @@ public class PhoneNumberPreferenceController extends BasePreferenceController {
             final Preference multiSimPreference = createNewPreference(screen.getContext());
             multiSimPreference.setOrder(phonePreferenceOrder + simSlotNumber);
             multiSimPreference.setKey(KEY_PHONE_NUMBER + simSlotNumber);
+            multiSimPreference.setSelectable(false);
             screen.addPreference(multiSimPreference);
             mPreferenceList.add(multiSimPreference);
         }