chore: prepare changelog for v0.12.21 (#1649)

Signed-off-by: itsomri <omric@nvidia.com>

Author: itsomri

CHANGELOG.md

@@ -6,6 +6,8 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/).
 
 ## [Unreleased]
 
+## [v0.12.21] - 2026-06-01
+
 ### Changed
 - Updated Go toolchain and base build images to v1.25.10.