Or not. The error continued even after doing that. Guess I'm glad I tested in dev first.
EDIT: Never mind. Something went wrong with the Process Designer again and it didn't take. I removed the action and added it again and this time the error stopped happening.
It appears this is some undocumented requirement for the Knowledge process and is best not to remove it. I may just end up hiding it since it really makes no sense to the analysts that see it.