Why do we terminate for spot fleets?

[emilymcafee]

If your Spot instance is interrupted in the middle of an instance hour because the Spot price exceeded your bid, you are not charged for the hour of use that was interrupted.

From the docs.

autoscaling.terminateInstanceInAutoScalingGroup makes sense, given that it comes with certain privileges, but for spot fleets we straight-up use ec2.terminate. Do we have any reason to keep this around? If not, let's remove it.

/cc @rclark @kellyoung