Update github action versions in test_release

The latest version of download-artifact v4 includes an important
security fix.

Version numbers of upload- and download- artifact are supposed to
match.

Other actions are already using these versions but this one was
overlooked.

.github/workflows/test_release.yml

@@ -36,7 +36,7 @@ jobs:
         run: python -m tox -c release_tox.ini
       - name: Upload test results
         if: always()
-        uses: actions/upload-artifact@v3
+        uses: actions/upload-artifact@v4
         with:
           name: Unit test results ${{ matrix.os }}
           path: tests_and_analysis/test/reports/junit_report*.xml
@@ -47,7 +47,7 @@ jobs:
     if: success() || failure()
     steps:
       - name: Download Artifacts
-        uses: actions/download-artifact@v2
+        uses: actions/download-artifact@v4
         with:
           path: artifacts
       - name: Publish test results