chore: remove codecov badge from readme (#5868)

README.md

@@ -6,7 +6,6 @@
 [![npm](https://img.shields.io/npm/v/@chainsafe/lodestar)](https://www.npmjs.com/package/@chainsafe/lodestar)
 [![Docker Image Version (latest by date)](https://img.shields.io/docker/v/chainsafe/lodestar?color=blue&label=Docker&sort=semver)](https://hub.docker.com/r/chainsafe/lodestar)
 [![Ethereum Consensus Spec v1.1.10](https://img.shields.io/badge/ETH%20consensus--spec-1.1.10-blue)](https://github.com/ethereum/consensus-specs/releases/tag/v1.1.10)
-[![codecov](https://codecov.io/gh/ChainSafe/lodestar/branch/unstable/graph/badge.svg)](https://codecov.io/gh/ChainSafe/lodestar)
 ![ES Version](https://img.shields.io/badge/ES-2020-yellow)
 ![Node Version](https://img.shields.io/badge/node-20.x-green)
 [![gitpoap badge](https://public-api.gitpoap.io/v1/repo/ChainSafe/lodestar/badge)](https://www.gitpoap.io/gh/ChainSafe/lodestar)