Fix codecov action config.

Author: davidlehn

.github/workflows/main.yml

@@ -71,7 +71,7 @@ jobs:
     - name: Upload coverage to Codecov
       uses: codecov/codecov-action@v5
       with:
-        file: ./test/coverage/lcov.info
+        files: ./test/coverage/lcov.info
         fail_ci_if_error: true
         token: ${{ secrets.CODECOV_TOKEN }}