revert(cats): Reverting the List -> Set change

[ajordens]

Seeing a couple oddities and want to ensure they're unrelated
(or related) to this change.

[spinnakerbot]

The following commits need their title changed:

188fda1: revert(cats): Reverting the List -> Set change

Seeing a couple oddities and want to ensure they're unrelated
(or related) to this change.

Please format your commit title into the form:

<type>(<scope>): <subject>, e.g. fix(kubernetes): address NPE in status check

This allows us to easily generate changelogs & determine semantic version numbers when cutting releases. You can read more about commit conventions here.