* fix: gets removedItem instead of its index
add: sliver_animated_list.0_test.dart

* fix: sliver_animated_list.0_test.dart

* fix: pr comments

* fix test import
Co-authored-by: Taha Tesser <tessertaha@gmail.com>

---------
Co-authored-by: Taha Tesser <tessertaha@gmail.com>