Fix false negatives in integration test for unused vars

Updated tests/integration/test_vars_usage_in_yaml.py:
- Variables immediately followed by '(' are now treated as function calls,
  not as set variables. This prevents false errors.
- Fixed detection of redirect_domain_mappings so it is no longer flagged
  as unused.

See: https://chatgpt.com/share/68c3542d-f44c-800f-a483-b3e43739f315

roles/web-opt-rdr-www/tasks/main.yml

@@ -10,7 +10,7 @@
   include_role:
     name: web-opt-rdr-domains
   vars:
-    domain_mappings: "{{ REDIRECT_WWW_DOMAINS | map('regex_replace', '^www\\.(.+)$', '{ source: \"www.\\1\", target: \"\\1\" }') | map('from_yaml') | list }}"
+    redirect_domain_mappings: "{{ REDIRECT_WWW_DOMAINS | map('regex_replace', '^www\\.(.+)$', '{ source: \"www.\\1\", target: \"\\1\" }') | map('from_yaml') | list }}"
   when: REDIRECT_WWW_FLAVOR == 'origin'
 
 - name: Include DNS role to set redirects