update changelog before v8.1.0 release

Author: crodriguezvega

CHANGELOG.md

@@ -34,14 +34,12 @@ Ref: https://keepachangelog.com/en/1.0.0/
 
 # Changelog
 
-## [Unreleased]
+## [v8.1.0](https://github.com/cosmos/ibc-go/releases/tag/v8.1.0) - 2024-01-31
 
 ### Dependencies
 
 * [\#5663](https://github.com/cosmos/ibc-go/pull/5663) Bump Cosmos SDK to v0.50.3 and CometBFT to v0.38.2.
 
-### API Breaking
-
 ### State Machine Breaking
 
 * (apps/27-interchain-accounts) [\#5442](https://github.com/cosmos/ibc-go/pull/5442) Increase the maximum allowed length for the memo field of `InterchainAccountPacketData`.