docs: remove stray 'build: rename workflow_dispatch input labels' from CHANGELOG

The auto-patch-release workflow included this bullet because 'build:' was treated as safe.
It's a CI label rename with no user-visible impact and shouldn't appear in the user-facing
CHANGELOG. Following work in extension-kit adds 'build:' to the default ignore regex so
future runs won't include such bullets.

Author: joshiste

CHANGELOG.md

@@ -2,7 +2,6 @@
 
 ## v1.5.9
 
-- build: rename workflow_dispatch input labels for the GH UI
 - chore(deps): runc 1.4.3 and dns-inject to v0.2.2
 - feat: set oom_score_adj directly via extension-kit (drop root subprocess) (#216)
 - fix: switch back to use strict root qdisc checks