Update codecov/codecov-action action to v6 (#28)

| datasource  | package                | from | to |
| ----------- | ---------------------- | ---- | -- |
| github-tags | codecov/codecov-action | v5   | v6 |

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

Author: renovate[bot]

.github/workflows/ci.yml

@@ -66,7 +66,7 @@ jobs:
 
       - name: "Send code coverage report to Codecov.io"
         if: ${{ matrix.code-coverage != 'none' }}
-        uses: "codecov/codecov-action@v5"
+        uses: "codecov/codecov-action@v6"
         with:
           token: ${{ secrets.CODECOV_TOKEN }}
           file: ./coverage.xml