Update actions/upload-artifact action to v6 (#822)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

.github/workflows/run_tests.yml

@@ -31,15 +31,15 @@ jobs:
           ./gradlew test jacocoTestReport
 
       - name: Upload Coverage Report
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v6
         if: always()
         with:
           name: coverage-report
           path: server/build/reports/jacoco/test/html/
           retention-days: 14
 
       - name: Upload Test Results
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v6
         if: always()
         with:
           name: test-results