Improve "Ensure that bump command exists"

[dsherret]

It would be good to improve this message. As a contributor to swc, I see the CI fails and then have to inspect the code of ensure-comment.ts wondering why it's failing. Maybe it could say there's nothing actionable the contributor needs to do (or ideally, I wonder if there's a way that this could be a pending status check until that comment occurs... I'm not familiar enough with GH actions)

[kdy1]

I want to make it pending, but I'm not sure the way to do it.
Btw, I agree that the error message should be improved

[kdy1]

I patched it to be Expected state before review.
This will not be rendered as an error by default. (If someone other than me reviews it, it will result in an error, though)

[kdy1]

I reverted the patch, because it requires a review comment after auto-rebase.