upstream CI: Disable ansible-lint var-naming check

Latest ansible-lint version (6.16.1) started to raise an error when
variable names from within roles are not prefixed with  the role name.
Error: var-naming[no-role-prefix].

As Ansible sanity check does not enforce this, it will be disabled, for
now on ansible-freeipa's upstream CI.

A future effort to reduce the checks that are not being evaluated should
be done as preparation for future Ansible Galaxy and Automation Hub
requirements.