Running older linter releases while we have a more up to date
Ansible 2.12 based linter does not provide value and thus wastes
ci resources. Our Ansible 2.9 based linter is broken atm and since
it is EOL soon anyway we drop this job. We still have a linter job
based on the last stable release and one based on Ansible's
devel branch.

Our tox environment for Ansible 2.9 will be dropped in a later
patch once all Ansible 2.9 based jobs have been removed.

Change-Id: I9cd3f729b06516bbd9a3c7985b65fcf294c8bdd7