roles: strict truthy values

According to Ansible we can use yes, true, True, "or any quoted st-
ring" for a boolean true, but ansible-lint wants us to use either
true or false.

See: https://chronicler.tech/red-hat-ansible-yes-no-and/

roles/common/tasks/ntp.yml

@@ -18,7 +18,7 @@
 
 - name: Start and enable systemd's NTP client
   when: ansible_service_mgr == 'systemd'
-  ansible.builtin.systemd: name=systemd-timesyncd state=started enabled=yes
+  ansible.builtin.systemd: name=systemd-timesyncd state=started enabled=true
 
 - name: Uninstall ntp on modern Ubuntu/Debian
   ansible.builtin.apt: name=ntp state=absent