Bump actions/upload-artifact from 3 to 4

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

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

Signed-off-by: dependabot[bot] <[email protected]>

.github/workflows/integration-test.yml

@@ -81,7 +81,7 @@ jobs:
         - name: Run mutant tests
           run: cargo mutants -vV --in-place
         - name: Archive results
-          uses: actions/upload-artifact@v3
+          uses: actions/upload-artifact@v4
           if: always()
           with:
             name: mutants-out