explicitly add CODECOV token to CI

https://discourse.julialang.org/t/psa-new-version-of-codecov-action-requires-additional-setup/109857

Author: bgctw

.github/workflows/CI.yml

@@ -47,6 +47,7 @@ jobs:
       - uses: codecov/codecov-action@v4
         with:
           file: lcov.info
+          token: ${{ secrets.CODECOV_TOKEN }}
   docs:
     name: Documentation
     runs-on: ubuntu-latest