Update manifest.md
Update manifest.md

Suggestion for text when the edition isn't defined at all
rust-lang/cargo,rustyhorde/cargo,nipunn1313/cargo,rustyhorde/cargo,rust-lang/cargo,nipunn1313/cargo,nipunn1313/cargo,eminence/cargo,rustyhorde/cargo,eminence/cargo,rust-lang/cargo,eminence/cargo,nipunn1313/cargo,eminence/cargo,rustyhorde/cargo,rust-lang/cargo