Auto merge of #8547 - ThePuzzlemaker:patch-1, r=ehuss
Auto merge of #8547 - ThePuzzlemaker:patch-1, r=ehuss

Include `+` for crates.io feature requirements in the Cargo Book section on features

This change was introduced in commit 5f842f7 of rust-lang/crates.io but was not subsequently added to the Cargo Book.

rust-lang/cargo,nipunn1313/cargo,nipunn1313/cargo,tshepang/cargo,tsurai/cargo,tshepang/cargo,tsurai/cargo,tsurai/cargo,rust-lang/cargo,eminence/cargo,tshepang/cargo,tsurai/cargo,nipunn1313/cargo,eminence/cargo,nipunn1313/cargo,rustyhorde/cargo,rust-lang/cargo,eminence/cargo,rustyhorde/cargo,rustyhorde/cargo,eminence/cargo,rustyhorde/cargo,rust-lang/cargo,tshepang/cargo,tsurai/cargo