chore(deps): update codecov/codecov-action action to v6

Author: renovate[bot]

.github/workflows/testing.yml

@@ -49,7 +49,7 @@ jobs:
         source .venv/bin/activate
         poetry run pytest --cov app
     - name: Upload coverage to Codecov
-      uses: codecov/codecov-action@v5
+      uses: codecov/codecov-action@v6
       with:
         verbose: true
       env: