Auto merge of #4419 - lzutao:ifchain-link, r=phansch
Auto merge of #4419 - lzutao:ifchain-link, r=phansch

Update if_chain doc link

changelog: none

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