Log open handles when process should be exiting.

[JAForbes]

For context: qgustavor/mega#132

I think this was just github actions runner not changing state, it happens. But just for absolute confidence it would be good to log any open handles when the pr-release CLI should be exiting.

There shouldn't be any handles but it is theoretically possible there's a timer or something else queued in octokit or zx that kept it running.