v2.13.0: fix go release version in changelog

CHANGELOG.md

 ### Internal
 
 * Upgraded the Docker base image from Alpine 3.13 to 3.19. The resulting images are incompatible with Docker 19.x and lower (all currently non-EOL Docker versions should be supported). (#2103)
-* Official release builds use Go 1.21.5
+* Official release builds use Go 1.21.6
 
 
 ## [2.12.0] - 2023-10-10