Update codecov/codecov-action action to v6

Author: renovate[bot]

.github/workflows/test.yml

@@ -27,7 +27,7 @@ jobs:
       - run: yarn --prefer-offline --frozen-lockfile
       - run: yarn test:ci
 
-      - uses: codecov/codecov-action@v5
+      - uses: codecov/codecov-action@57e3a136b779b570ffcdbf80b3bdc90e7fab3de2 # v6
 
       - uses: tryghost/actions/actions/slack-build@main
         if: failure() && github.event_name == 'push' && github.ref == 'refs/heads/main'