Bot sometimes removes PRs from board when it should not

[jasongrout]

This run removed jupyterhub/binderhub#1348 from the jupyterhub board when it should not have removed it. The next run a few minutes later added that PR back on to the PR triage board.

I'm not sure why it was removed. I don't see any action on the PR (such as closing it) that would have caused its removal. Some possibilities:

1. The query api could have messed up and not given us the PR in the first run. Perhaps there was a problem with the paging?
2. (more likely) There is some bug in our code that checks if prs on the board are still active

I'm not sure this is very actionable at this point, other than examining our code for bugs that would miss active PRs. I just wanted to log this issue in case we see it again.

I do notice that PR had its board status field manually changed (but like a month ago). That may be related, though it seems unlikely since we've run this bot many, many times since the status was changed.

[jasongrout]

CC @yuvipanda, since you had manually set the board status field for jupyterhub/binderhub#1348, but now the status is now cleared since the pr was removed and added back fresh.