Update codecov/codecov-action action to v6

Author: renovate[bot]

.github/workflows/test.yml

@@ -78,6 +78,6 @@ jobs:
       - name: Run unit tests
         run: make test
       - name: Upload coverage reports to Codecov
-        uses: codecov/codecov-action@v5
+        uses: codecov/codecov-action@v6
         env:
           CODECOV_TOKEN: ${{ secrets.CODECOV_TOKEN }}