ci: bump remaining outdated Actions versions

ci: bump remaining outdated Actions versions

After activating automatic Dependabot updates in the
git-for-windows/git repository, Dependabot noticed a couple
of yet-unaddressed updates.  They avoid "Node.js 16 Actions"
deprecation messages by bumping the following Actions'
versions:

- actions/upload-artifact from 3 to 4
- actions/download-artifact from 3 to 4
- actions/cache from 3 to 4

Helped-by: Matthias Aßhauer <redacted>
Signed-off-by: Johannes Schindelin <redacted>
Signed-off-by: Junio C Hamano <redacted>