[setup] fix min isort requirements
the current isort min version requirement doesn't match CI's reality

even with isort 5.10.1 `make style` leads to modified code which doesn't match CI.

I tested that 5.12 syncs with CI.

no, actually that didn't help :(<|||||>The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/transformers/pr_25126). All of your documentation changes will be reflected on that endpoint.