Fix channel configurability check

Test: atest
Fixes: 128669244
Change-Id: Ib4bc666262426ea1fb8fc034a361c93bdd5afb36

src/com/android/settings/notification/NotificationPreferenceController.java

@@ -111,6 +111,9 @@ public abstract class NotificationPreferenceController extends AbstractPreferenc
     }
 
     protected boolean isChannelConfigurable() {
+        if (mAppRow != null && mAppRow.lockedImportance) {
+            return false;
+        }
         if (mChannel != null && mAppRow != null) {
             return !Objects.equals(mChannel.getId(), mAppRow.lockedChannelId);
         }