Update codecov/codecov-action action to v6

Author: renovate[bot]

.github/workflows/build.yml

@@ -43,7 +43,7 @@ jobs:
       - name: Run tests with coverage
         run: python -m pytest --cov --cov-branch --cov-report=xml
       - name: Upload coverage to Codecov
-        uses: codecov/codecov-action@v5
+        uses: codecov/codecov-action@v6
         with:
           token: ${{ secrets.CODECOV_TOKEN }}
           fail_ci_if_error: true