Add CHANGELOG entry for FFI and port_ocaml removal

Co-authored-by: dannywillems <[email protected]>

Author: Copilot

CHANGELOG.md

@@ -25,6 +25,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Removed
 
+- **Ledger**: remove FFI codebase and `port_ocaml` module, fix
+  [#1235](https://github.com/o1-labs/mina-rust/issues/1235)
 - **Frontend**: remove outdated `frontend/functions` directory containing unused
   Firebase Cloud Functions
 - **CI**: remove network debugger from CI