Fix link to hello-cargo in the book
Fix link to hello-cargo in the book

It was moved in #29538.

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