bors should not close pull requests

[SimonSapin]

When a set of builds/tests pass, bors appears to explicitly close the corresponding pull-request. Is there a reason to do this? If it didn’t, GitHub would automatically mark the PR as "Merged" (which is nicer than "Closed") when bors merges into master and the commit ends up in HEAD’s ancestry.

[pnkfelix]

bors repo: https://github.com/graydon/bors

[SimonSapin]

Thanks @pnkfelix. Closing in favor of graydon/bors#14