rl-2505: ndppd: mention default rule method change

Signed-off-by: 谢致邦 (XIE Zhibang) <[email protected]>

nixos/doc/manual/release-notes/rl-2505.section.md

@@ -338,6 +338,8 @@
 
 - `programs.fzf.keybindings` now supports the fish shell.
 
+- `services.ndppd.proxies.<name>.rules.<name>.method` now defaults to "static".
+
 <!-- To avoid merge conflicts, consider adding your item at an arbitrary place in the list instead. -->
 
 ## Nixpkgs Library {#sec-release-25.05-lib}