[TASK] Adjust ACL migration to cover content security
This is a follow-up to the "Restructure policy component to new
Policy.yaml format" change (I84e188e89a05ec0dd1f9ee96fe312dac81806759)
that adjusts the provided core migration to cover "entities" resources
too. Previously a warning was shown when applying the core migration
to ``Policy.yaml`` files that contained resources of type "entities".
Releases: master, 3.0