chore(deps): update actions/upload-artifact action to v6

Author: renovate[bot]

.github/workflows/ci.yml

@@ -96,7 +96,7 @@ jobs:
           files: lcov.info
 
       - name: Archive code coverage results
-        uses: actions/upload-artifact@v5
+        uses: actions/upload-artifact@v6
         with:
           name: code-coverage-report
           path: lcov.info