Bump actions/upload-artifact from 5 to 6 (#218)

Bumps [actions/upload-artifact](https://github.com/actions/upload-artifact) from 5 to 6.
- [Release notes](https://github.com/actions/upload-artifact/releases)
- [Commits](actions/upload-artifact@v5...v6)

---
updated-dependencies:
- dependency-name: actions/upload-artifact
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

.github/workflows/ci.yml

@@ -151,7 +151,7 @@ jobs:
         run: bin/rails db:test:prepare test:system
 
       - name: Keep screenshots from failed system tests
-        uses: actions/upload-artifact@v5
+        uses: actions/upload-artifact@v6
         if: failure()
         with:
           name: screenshots