Adding 2.9 ignore allow-list for sanity rule

[alisonlhart]

Note: This is an extremely opinionated rule that Partner Engineering enforces for certified content.

Modifying new rule sanity to add an allow-list for Ansible 2.9 (ignore-2.9.txt files).
Allowed ignores added:
validate-modules:deprecation-mismatch
validate-modules:invalid-documentation

Also added the action-plugin-docs ignore to the all allow list.

These were added at the request of the Networking collections' maintainers.

Note: the eco test will fail, until the arguments-renamed ignore is removed from the collection ignore files.