bors squash does not close PRs

[RalfJung]

See rust-lang/miri#2541: a PR merged with bors squashing does not get closed.

[kellda]

I think the only way to fix this is to have bors force-push the squased commit to the PR's branch

[klensy]

Partial copypaste from #182:
This also left stray commit in bors gh history, and if noone wants to fix that squash for now, it better be disabled (that change should be easy?).

[kellda]

I'm not sure to understand the problem. Do you mean that the "fix verbatim with upstream dependencies" commit should not belong to bors ? If that's what you mean, then it's #136. Is there still another way it behaves unexpectedly ?