Only admin users may change private DNS settings

Bug: 237289258
Test: manual
Change-Id: Ia2875fb8c628642daebc48fc6aec99aaf30e64be

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

@@ -89,8 +89,8 @@ public class PrivateDnsPreferenceController extends BasePreferenceController
             return UNSUPPORTED_ON_DEVICE;
         }
         final UserManager userManager = mContext.getSystemService(UserManager.class);
-        if (userManager.isGuestUser()) return DISABLED_FOR_USER;
-        return AVAILABLE;
+        if (userManager.isAdminUser()) return AVAILABLE;
+        return DISABLED_FOR_USER;
     }
 
     @Override