Update the coverage badge to use the correct link (#148)

Author: AhmedHanafy725

README.md

@@ -1,6 +1,6 @@
 # tfgrid-sdk-dart
 
-[![melos](https://img.shields.io/badge/maintained%20with-melos-f700ff.svg?style=flat-square)](https://github.com/invertase/melos) [![codecov](https://codecov.io/gh/codescalers/tfgrid-sdk-dart/graph/badge.svg?token=O34UDTMW5O)](https://codecov.io/gh/codescalers/tfgrid-sdk-dart)
+[![melos](https://img.shields.io/badge/maintained%20with-melos-f700ff.svg?style=flat-square)](https://github.com/invertase/melos) [![codecov](https://codecov.io/gh/threefoldtech/tfgrid-sdk-dart/graph/badge.svg?token=KrlhzzdP72)](https://codecov.io/gh/threefoldtech/tfgrid-sdk-dart)
 
 This repo contains the dart clients for Threefold grid.