Revert codecov-action to v3

Author: bouwew

.github/workflows/verify.yml

@@ -331,7 +331,7 @@ jobs:
           coverage report --fail-under=94
           coverage xml
       - name: Upload coverage to Codecov
-        uses: codecov/codecov-action@v4
+        uses: codecov/codecov-action@v3
 
   test-publishing:
     name: Build and publish Python 🐍 distributions 📦 to TestPyPI