CI: Update to isort 5

[AlexKirko]

isort 5.x is out with some changes to how it sorts. We'll need to update the code and unpin in our environment file.

[jreback]

love a PR to fix (can likely just drop the recursive kw) or could pin isort- either way us ok

[AlexKirko]

Should be fine if we drop the keyword. Let me give it a try.

[AlexKirko]

take

[AlexKirko]

Yeah, no. Version 5 has changed the way it sorts imports, so it now throws a couple hundred errors on our file base. I'll pin isort for now, and we can check later if this new version breaks anything.