Fix Dismiss button not appearing in promoted guts

The isNonBlockable and isDismissable booleans were inverted, which had
two unintended effects:
- the dismiss button wasn't being shown anymore
- we were also hiding the "Turn off" button, and showing the "These
  notifications can't be modified" text

Bug: 412579162
Test: manual
Flag: com.android.systemui.permission_helper_ui_rich_ongoing
Change-Id: I09aa1b194b9f657b2dd8eb5e5df6e813f8ec82c5