Lower Python version requirement to any Python 3 version

This is because otherwise we'll fail to install on any system not explicitly running Python 3.7 (like some Debian we provision Arch on).
We don't strictly need Python 3.7 and most Python 3 versions will in fact work with Ansible.

group_vars/all/common.yml

@@ -5,7 +5,7 @@ configure_firewall: true
 
 # this is needed to make ansible find the firewalld python
 # module when deploying firewalld tasks
-ansible_python_interpreter: /usr/bin/python3.7
+ansible_python_interpreter: /usr/bin/python3
 
 zabbix_agent_templates:
   - Template OS Linux