[skip ci] Update changelogs for v0.21.3 release

GitOrigin-RevId: 2e2397508ebd54e59a9557718bbfe535ec0d26cc

Author: github-actions[bot]

CHANGELOG.md

@@ -4,6 +4,8 @@ Mapbox welcomes participation and contributions from everyone.
 
 ## main
 
+## 11.21.3 - 23 April, 2026
+
 ## 11.21.2 - 16 April, 2026
 
 ## 11.21.1 - 10 April, 2026