Bump minimium Ansible version to 2.7.1

Provoked by #743

docs/ansible.md

@@ -9,7 +9,7 @@ If your local computer cannot run Ansible, you can also run Ansible on some serv
 
 ## Supported Ansible versions
 
-Ansible 2.7.0 or newer is required.
+Ansible 2.7.1 or newer is required ([last discussion about Ansible versions](https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/743)).
 
 Note: Ubuntu 20.04 ships with Ansible 2.9.6 which is a buggy version (see this [bug](https://bugs.launchpad.net/ubuntu/+source/ansible/+bug/1880359)), which can't be used in combination with a host running new systemd (more details in [#517](https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/517), [#669](https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/669)). If this problem affects you, you can: avoid running Ubuntu 20.04 on your host; run Ansible from another machine targeting your host; or try to upgrade to a newer Ansible version (see below).