bors takes credit for squashed PRs

bors takes authorship credit for `@bors squash` PRs: https://github.com/rust-lang/rust/commit/4b806878549990d2ad2aa3c265751d3d89947cdf (PR is https://github.com/rust-lang/rust/pull/81398).

Also, not sure if this is related, but GitHub doesn't realize the PR is merged when bors squash-merges it (you can see an example in the same PR).