CHANGELOG.md: refer to correct pull requests

Author: Mic92

CHANGELOG.md

@@ -7,7 +7,7 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 
 <!--### Added-->
 - Added `nix::unistd::{openat, fstatat, readlink, readlinkat, rename, renameat, mknodat, unlinkat, mkdirat, link, linkat, symlink, symlinkat}`
-  ([#497](https://github.com/nix-rust/nix/pull/551))
+  ([#552](https://github.com/nix-rust/nix/pull/552), [#561](https://github.com/nix-rust/nix/pull/561))
 
 ### Changed
 - Marked `sys::mman::{ mmap, munmap, madvise, munlock, msync }` as unsafe.