Revert "Update codecov/codecov-action action to v4 (#226)"

This reverts commit 0718b49.

Author: daohoangson

.github/workflows/flutter.yml

@@ -40,7 +40,7 @@ jobs:
         with:
           name: failures
           path: "**/failures/*.png"
-      - uses: codecov/codecov-action@v4
+      - uses: codecov/codecov-action@v3
 
   build_apk:
     if: ${{ github.ref == 'refs/heads/master' || contains(github.ref, 'android') }}