Bump version for upload-artifact GH action #1540
Description
As with
we need to update the version of that action, and failing to do so will likely block our release process. There are a number of uses of it in this repo, and we should bring them all up to v4. Find them here: https://github.com/search?q=repo%3Acmu-delphi%2Fdelphi-epidata%20path%3A%2F%5E%5C.github%5C%2F%2F%20upload-artifact&type=code