fix(devops):fixed incorrect url for codecov status badge (#616)

Author: cnlangzi

README.md

@@ -2,7 +2,7 @@
 [![Build](https://github.com/0chain/blobber/actions/workflows/build-&-publish-docker-image.yml/badge.svg)](https://github.com/0chain/blobber/actions/workflows/build-&-publish-docker-image.yml)
 [![Test](https://github.com/0chain/blobber/actions/workflows/tests.yml/badge.svg)](https://github.com/0chain/blobber/actions/workflows/tests.yml)
 [![GoDoc](https://godoc.org/github.com/0chain/blobber?status.png)](https://godoc.org/github.com/0chain/blobber)
-[![codecov](https://codecov.io/gh/0chain/blobber/branch/main/graph/badge.svg)](https://codecov.io/gh/0chain/blobber)
+[![codecov](https://codecov.io/gh/0chain/blobber/branch/staging/graph/badge.svg)](https://codecov.io/gh/0chain/blobber)
 
 # Blobber Setup
 This readme provide instructions on how to run blobber locally