Removes all assignees incorrectly #177
Description
If a user is assigned using the GitHub UI, they shouldn't be unassigned by zulipbot, but that's what happened for zulip/zulip#15416 where I had assigned myself 5 days prior to being automatically removed with the other contributor.
We can use https://chat.zulip.org/#narrow/stream/105-zulipbot/topic/removing.20all.20assignees for discussion.