readme: remove circleci status

Closes: aptos-labs#7258

README.md

@@ -7,7 +7,6 @@
 ---
 
 [![Diem Rust Crate Documentation (master)](https://img.shields.io/badge/docs-master-59f)](https://diem.github.io/diem/)
-[![CircleCI](https://circleci.com/gh/diem/diem.svg?style=shield)](https://circleci.com/gh/diem/diem)
 [![License](https://img.shields.io/badge/license-Apache-green.svg)](LICENSE)
 [![grcov](https://img.shields.io/badge/Coverage-grcov-green)](https://ci-artifacts.diem.com/coverage/unit-coverage/latest/index.html)
 [![codecov](https://codecov.io/gh/diem/diem/branch/master/graph/badge.svg)](https://codecov.io/gh/diem/diem)