Update link to Cargo manifest documentation

Author: dtolnay

_src/README.md

@@ -94,7 +94,7 @@ Serde by the community.
 [Starlark]: https://github.com/dtolnay/serde-starlark
 [Envy]: https://github.com/softprops/envy
 [Envy Store]: https://github.com/softprops/envy-store
-[Cargo]: http://doc.crates.io/manifest.html
+[Cargo]: https://doc.rust-lang.org/cargo/reference/manifest.html
 [AWS Parameter Store]: https://docs.aws.amazon.com/systems-manager/latest/userguide/systems-manager-parameter-store.html
 [S-expressions]: https://github.com/rotty/lexpr-rs
 [D-Bus]: https://docs.rs/zvariant