CLA bot broken

Created by: slimsag

Our CLA bot is broken currently. See this thread for details: https://sourcegraph.slack.com/archives/C07KZF47K/p1570046864137300

It is broken because it cannot sync the issues:

2019/10/02 23:14:49 corpus.Sync: GET https://api.github.com/repos/sourcegraph/sourcegraph/issues/2921: 410 This issue was deleted []; sleeping 15s

This is due to golang.org/x/build/maintner not supporting closed GitHub issues. It is weird that GitHub decided to implement this as a 410 status instead of using a field similar to how they denote closed and other statuses, but nonetheless maintner cannot handle it and bails out.

We will need to fix that issue upstream here in the code: https://github.com/golang/build/blob/c41ee31c2ed1caabb143ad39d536b27087620bfc/maintner/github.go#L1841-L1861 and then rebuild and redeploy sgbot with the new version for it to start working again.