Finish migration to role instead of `is_admin` (#9414)

Release Notes:

- Fixed a bug signing in for five users
([#4323](https://github.com/zed-industries/zed/issues/4323)).
dd33330648Conrad Irwin committed on 3/15/2024, 7:04:48 PM· committed by GitHubparent123d3ee
3 files changedLine totals unavailable