delete ~Stale removal action

This would cancel out the Stale label addition, because then the next time the bot runs it would cound that as activity and delete the label.

An example of this is visible here:

team#40409 (comment 2763207)

We would need some custom code to check the author of the action and ignore the triage bot. I can't be bothered to write some Ruby right now, so this is the simpler way.