Remove isort from pre-commit hook

[mknaranja]

As this issue PyCQA/isort#2068 is not resolved. I will remove isort from the pre-commit hook. We will have to ensure from time to time that everything is well sorted but with my workflow of worktrees isort does not fit at all and even leads to a lot of wrongly checked out branches as you have to free the WIP branch before being able to apply the hook on the main worktree of the hard disk.