[inherit_parent_scenario] Fix loop variable type for Ansible 2.16

Convert _file_list to YAML to ensure loop receives a list type instead
of string. Ansible 2.16+ enforces strict type checking for loop values.

Co-Authored-By: Claude <noreply@anthropic.com>
Signed-off-by: Sergii Golovatiuk <sgolovat@redhat.com>

Author: 2 people

ci/playbooks/tasks/inherit_parent_scenario.yml

@@ -27,4 +27,4 @@
     - item is exists
   ansible.builtin.include_vars:
     file: "{{ item }}"
-  loop: "{{ _file_list }}"
+  loop: "{{ _file_list | from_yaml }}"