replaced 'ansible_os_platform' to 'ansible_os_family' (#44676)

replaced 'ansible_os_platform' to 'ansible_os_family' as 'ansible_os_platform' variable is no longer available.

docs/docsite/rst/user_guide/playbooks_reuse_roles.rst

@@ -46,9 +46,9 @@ Other YAML files may be included in certain directories. For example, it is comm
     # roles/example/tasks/main.yml
     - name: added in 2.4, previously you used 'include'
       import_tasks: redhat.yml
-      when: ansible_os_platform|lower == 'redhat'
+      when: ansible_os_family|lower == 'redhat'
     - import_tasks: debian.yml
-      when: ansible_os_platform|lower == 'debian'
+      when: ansible_os_family|lower == 'debian'
 
     # roles/example/tasks/redhat.yml
     - yum: