Bump actions/download-artifact from 3 to 4 (#931)

Bumps [actions/download-artifact](https://github.com/actions/download-artifact) from 3 to 4.
- [Release notes](https://github.com/actions/download-artifact/releases)
- [Commits](https://github.com/actions/download-artifact/compare/v3...v4)

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

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

.github/workflows/benchstat.yml

@@ -66,11 +66,11 @@ jobs:
       - name: Install benchstat
         run: go get -u golang.org/x/perf/cmd/benchstat
       - name: Download Incoming
-        uses: actions/download-artifact@v3
+        uses: actions/download-artifact@v4
         with:
           name: bench-incoming
       - name: Download Current
-        uses: actions/download-artifact@v3
+        uses: actions/download-artifact@v4
         with:
           name: bench-current
       - name: Benchstat Results