Remove outdated CircleCI badge

Author: LukeMathWalker

README.md

@@ -2,7 +2,6 @@
 [![Releases](https://img.shields.io/github/release/RedisLabsModules/redismodule-rs.svg)](https://github.com/RedisLabsModules/redismodule-rs/releases/latest)
 [![crates.io](https://img.shields.io/crates/v/redis-module.svg)](https://crates.io/crates/redis-module)
 [![docs](https://docs.rs/redis-module/badge.svg)](https://docs.rs/redis-module)
-[![CircleCI](https://circleci.com/gh/RedisLabsModules/redismodule-rs/tree/master.svg?style=svg)](https://circleci.com/gh/RedisLabsModules/redismodule-rs/tree/master)
 
 # redismodule-rs