Remove league/flysystem-bundle dependency

## Description

- Remove FileFetchTask, use cleverage/flysystem-process-bundle instead.
- Remove league/flysystem-bundle dependency on composer.json. 

## Requirements

* Documentation updates
  - [ ] Reference
  - [ ] Cookbooks
  - [X] Changelog
* [ ] Unit tests 

## Breaking changes

- Remove FileFetchTask, use cleverage/flysystem-process-bundle instead.
