fix: remove codecov badge

Author: BelfordZ

README.md

@@ -3,7 +3,6 @@
 <center>
   <span>
     <img alt="CircleCI branch" src="https://img.shields.io/circleci/project/github/open-rpc/meta-schema/master.svg">
-    <img src="https://codecov.io/gh/open-rpc/meta-schema/branch/master/graph/badge.svg" />
     <img alt="Dependabot status" src="https://api.dependabot.com/badges/status?host=github&repo=open-rpc/meta-schema" />
     <img alt="Chat on Discord" src="https://img.shields.io/badge/chat-on%20discord-7289da.svg" />
     <img alt="npm" src="https://img.shields.io/npm/dt/@open-rpc/meta-schema.svg" />