[skip ci] fix CHANGELOG for addition of nmount

Reported by:	Anthony Ramine <@nox>

CHANGELOG.md

@@ -7,7 +7,7 @@ This project adheres to [Semantic Versioning](https://semver.org/).
 ### Added
 - Added `if_nameindex` (#[1445](https://github.com/nix-rust/nix/pull/1445))
 - Added `nmount` for FreeBSD.
-  (#[1447](https://github.com/nix-rust/nix/pull/1447))
+  (#[1453](https://github.com/nix-rust/nix/pull/1453))
 - Added `IpFreebind` socket option (sockopt) on Linux, Fuchsia and Android.
   (#[1456](https://github.com/nix-rust/nix/pull/1456))
 - Added `TcpUserTimeout` socket option (sockopt) on Linux and Fuchsia.