Rollup merge of #63314 - tshepang:update-src-readme, r=matthewjasper
Rollup merge of #63314 - tshepang:update-src-readme, r=matthewjasper

doc: the content has since been moved to the guide

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