Update codecov/codecov-action action to v6

Author: renovate[bot]

.github/workflows/tests.yml

@@ -129,7 +129,7 @@ jobs:
 
       # https://github.com/codecov/codecov-action
       - name: Upload coverage results to Codecov
-        uses: codecov/codecov-action@v5
+        uses: codecov/codecov-action@v6
         env:
           CODECOV_TOKEN: ${{ secrets.CODECOV_TOKEN }}
         with: