docs: add CHANGELOG entry for billing removal

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: brendan-kellam

CHANGELOG.md

@@ -7,6 +7,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Removed
+- [EE] Removed Stripe billing integration, including subscription management, billing UI, and related database schema [#1069](https://github.com/sourcebot-dev/sourcebot/pull/1069)
+
 ## [4.16.4] - 2026-04-01
 
 ### Added