[yt-dev] headsup: new dependencies

Hi yt-dev Headsup: In order to facilitate downstream packaging, we’re dropping the unmaintained `toml` library as a dependency and switching to tomli + tomli_w instead See https://github.com/yt-project/yt/pull/3830 for context and https://github.com/yt-project/yt/pull/3831 for the change. This may break your dev env if you don’t have these packages installed already, so beware that you may need to fix that soon when you pull from yt’s main branch. Cheers Clément