chore: update changelog for v2.1.0

Author: k-yang

CHANGELOG.md

@@ -38,7 +38,7 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
-## [Unreleased]
+## [v2.1.0](https://github.com/NibiruChain/nibiru/releases/tag/v2.1.0) - 2025-02-25
 
 - [#2104](https://github.com/NibiruChain/nibiru/pull/2104) - chore: update chain IDs
 - [#2202](https://github.com/NibiruChain/nibiru/pull/2202) - chore(build): add build tags and missing flags/variables