CI: Remove isort from CI dependencies

[datapythonista]

In #25455 we added isort as a dependency to all our builds. Looks like the CI was failing, and adding isort fixed the problem. Not sure what the problem is, but isort is something we should only have in environment.yml, as it's only used in ci/code_checks.sh and locally.

We should remove isort from all files in ci/deps/ and if the CI complains, find out what's the problem, and fix it.

[alimcmaster1]

Currently taking a look :)