Add CHANGELOG entry for Link::get_fd() removal

This change adds a CHANGELOG entry for the removal of the deprecated
Link::get_fd() method, which we forgot to add earlier.

Signed-off-by: Daniel Müller <[email protected]>

Author: d-e-s-o

libbpf-rs/CHANGELOG.md

@@ -8,6 +8,7 @@ Unreleased
   - Added `Map::info` to `Map` to make it easier to derive `MapInfo` from a
     `Map` instance
 - Added `set_log_level`, `log_level`, and `autoload` methods to `OpenProgram`
+- Remove deprecated `Link::get_fd` method
 - Bumped minimum Rust version to `1.63`