Are you in Personal Projects by any chance?
We’re actually in the process of deprecating Personal Projects and because we’re no longer maintaining them, there are some bugs, e.g., removed users stay in the typeahead.
If this is the case (and the bug is annoying enough to you), I’d recommend creating a new Workspace for yourself. If you’re not in Personal Projects, can you take a screenshot of your Workspace Settings where you have your member list?