Fix change_freeze boolean coercion in preflight assert

roles/preflight/tasks/main.yml

@@ -2,7 +2,7 @@
 - name: Check change freeze
   ansible.builtin.assert:
     that:
-      - change_freeze == false
+      - not (change_freeze | bool)
     fail_msg: "FROZEN: {{ inventory_hostname }} is under a change freeze. Aborting."
     success_msg: "Change freeze check passed"