CI: Remove 'warn:' that's removed in ansible-core 2.14 (#4434)

* Remove 'warn:' that's removed in ansible-core 2.14.

* Install virtualenv when needed.

tests/integration/targets/monit/tasks/main.yml

@@ -43,6 +43,18 @@
       src: httpd_echo.py
       dest: "{{ process_file }}"
 
+  - name: Install virtualenv
+    package:
+      name: virtualenv
+      state: present
+    when: ansible_distribution == 'CentOS' and ansible_distribution_major_version == '8'
+
+  - name: Install virtualenv
+    package:
+      name: python-virtualenv
+      state: present
+    when: ansible_os_family == 'Archlinux'
+
   - name: install dependencies
     pip:
       name: "{{ item }}"