Update validate_config.yml files: edit the banner message for variables name

Signed-off-by: Suguru Hirahara <acioustick@noreply.codeberg.org>

roles/custom/matrix-base/tasks/validate_config.yml

@@ -19,7 +19,7 @@
   ansible.builtin.fail:
     msg: >-
       Your configuration contains a variable, which now has a different name.
-      Please change your configuration to rename the variable (`{{ item.old }}` -> `{{ item.new }}`).
+      Please rename the variable (`{{ item.old }}` -> `{{ item.new }}`) on your configuration file (vars.yml).
   when: "item.old in vars"
   with_items:
     - {'old': 'host_specific_hostname_identity', 'new': 'matrix_domain'}