Use secret token for Codecov upload

Author: mmoll

.github/workflows/ci.yml

@@ -102,9 +102,10 @@ jobs:
         if: ${{ matrix.os == 'windows-latest' }}
         run: vendor/bin/phan --allow-polyfill-parser
       - name: Upload coverage to Codecov
-        uses: codecov/codecov-action@v3
+        uses: codecov/codecov-action@v5
         with:
           verbose: true
+          token: ${{ secrets.CODECOV_TOKEN }}
 
   slack-notify:
     needs: [run-tests, style-checks]