[autohold playbook] Add missing bracket

#2607
missed a bracket and that results into an error.

Related-Issue: OSPRH-12508

Author: karelyatin

ci/playbooks/multinode-autohold.yml

@@ -29,7 +29,7 @@
             _zuul_api_url: >-
               {{
                 [
-                  ('https://'+ _zuul_host,
+                  ('https://'+ _zuul_host),
                   'zuul',
                   'api',
                   'tenant',