Add Codecov token

.github/workflows/checks.yml

@@ -73,6 +73,8 @@ jobs:
         env:
           NODE_OPTIONS: --max_old_space_size=4096
       - uses: codecov/codecov-action@v3
+        with:
+          token: ${{ secrets.CODECOV_TOKEN }}
 
   slither:
     if: github.repository != 'OpenZeppelin/openzeppelin-contracts-upgradeable'