Fix the name of a channel of discord in CONTRIBUTING.md
Fix the name of a channel of discord in CONTRIBUTING.md

graydon/rust,aidancully/rust,aidancully/rust,graydon/rust,aidancully/rust,graydon/rust,graydon/rust,graydon/rust,aidancully/rust,aidancully/rust,graydon/rust,aidancully/rust