chore(repo): group download & upload artifact updates

Pull request checklist

Please check if your PR fulfills the following requirements:

[ ] Docs have been reviewed and added / updated if needed (for bug fixes / features)
[ ] Build (npm run build) was run locally and any changes were pushed
[ ] Tests (npm test) were run locally and passed
[x] Prettier (npm run prettier) was run locally and passed

Pull request type

Please check the type of change your PR introduces: - [ ] Bugfix - [ ] Feature - [ ] Refactoring (no functional changes, no api changes) - [ ] Build related changes - [ ] Documentation content changes - [x] Other (please describe): renovate config ## What is the current behavior?

We upgrade the upload-artifact and download-artifact actions separately, which leads to more testing than needed.

GitHub Issue Number: N/A

What is the new behavior?

update the renovate configuration to group actions/download-artifact and actions/upload-artifact. these two should be upgraded at the same time, as they can rely on one another when it comes to major version bumps.

the configuration here was taken from https://github.com/ionic-team/stencil/blob/ea8d29b010ee2d4e0a43e50b0c59364c1e002fc5/renovate.json5#L82-L86

Does this introduce a breaking change?

[ ] Yes
[x] No

Testing

Locally, I ran renovate-config-validator, which is about all we can do here.

ionic-team / stencil-sass