[CI] Fix yarn cache

[fzaninotto]

The dependency installation never manages to store cache.

See e.g. https://github.com/marmelab/react-admin/actions/runs/8945903962/job/24575813530

saving npm cache failed with Error: Path Validation Error: Path(s) specified in the action for caching do(es) not exist, hence no cache is being saved., continuing...

After various tries, I still don't manage to get the cache working.

So I raised an issue in the @bahmutov/npm-install action repo (https://github.com/bahmutov/npm-install/issues/216#issuecomment-2093883821)