federation-api: Fix link to old matrix-doc repo
//! Endpoint to receive metadata about implemented matrix versions.
pub mod msc3723 {
- //! [GET /_matrix/federation/versions](https://github.com/matrix-org/matrix-doc/pull/3723)
+ //! [GET /_matrix/federation/versions](https://github.com/matrix-org/matrix-spec-proposals/pull/3723)
use ruma_common::api::ruma_api;
