Auth breaks after fly auto-updates if $FLY_AUTH_TOKEN is set

[Erich-Marais]

Describe the bug Fly auto-upgraded (not sure what the previous version was) and then auth broke (wouldn't let me deploy). Logging out and back in didn't work.

• Operating system: Windows 10 pro, build 19045.5608
• fly version fly.exe v0.3.91

** Command output: **

#>fly auth login
successfully logged in as *******
>fly auth whoami
Error: failed retrieving current user: You must be authenticated to view this.

I thought it might have something to do with the $FLY_AUTH_TOKEN environment variable, and unsetting that fixed it, but I feel it should not have broken in the first place