Update chokidar to v4

First things first: I am aware that karma is deprecated but I think this has relevance nonetheless.

Chokidar v4 dropped 11 dependencies and karma still gets a solid 11.6 million downloads per month.
As part of the ecosystem cleanup initiative (https://e18e.dev), we try to modernize the ecosystem by reducing bloat, updating old deps and reducing traffic.
I think even tho karma is eol, updating chokidar is a sensible thing to do. It enables all your users (who stick with it for one or the other reason) to install karma just a bit faster.

I would be happy to create a PR for this change if you are up for it.

Locate the chokidar dependency in the repository's dependency manifest and check the lockfile if present. Update it to v4, then run dependency installation and the existing test suite to confirm Karma still works with the newer dependency.

Written by the indexing model from the issue text.