Add ansible-compat to denylist

ansibe-compat is pulled in by ansible-lint[1] while also being in use by
molecule [2].

Latest release of ansibe-compat does break currently existing molecule
version which results in molecule to fail installing internal galaxy
requirements[3]

Thus, we need to be able to limit maximum version of ansible-compat
for testing. As all other ansible requirements are defined in denylist,
it makes sense to extend it with ansible-compat as well

[1] https://github.com/ansible/ansible-lint/blob/6178262c7e0d5e9792b5990d40029047760b8f09/.config/requirements.in#L4
[2] https://github.com/ansible/molecule/blob/23200bc984a8f9eb4bc5c20f7292632b75ca52c5/.config/requirements.in#L1
[3] https://zuul.opendev.org/t/openstack/build/4168176ce1a646a79235bbe3e1bf17ed/log/job-output.txt#1020

Needed-By: https://review.opendev.org/c/openstack/openstack-ansible/+/939274
Change-Id: I56e203007c491cb247435f3b8e5320ca2852a9ab

Author: Dmitriy Rabotyagov

denylist.txt

@@ -37,6 +37,7 @@ vmware-nsxlib
 
 # Projects are free to specify their own version of ansible and molecule
 ansible
+ansible-compat
 ansible-core
 molecule
 molecule-plugins