Update CHANGELOG.md

Removed outdated changelog entries and fixed formatting.

Author: brendan-kellam

CHANGELOG.md

@@ -9,11 +9,6 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 - Upgraded `seroval` to `^1.5.6`. [#1508](https://github.com/sourcebot-dev/sourcebot/pull/1508)
-
-### Changed
-- Vulnerability triage now keeps Linear issues synchronized with current security findings.
-
-### Fixed
 - Fixed vulnerability triage for reusable-workflow callers, repositories without CodeQL, and transient non-JSON Linear query responses. [#1515](https://github.com/sourcebot-dev/sourcebot/pull/1515)
 
 ## [5.1.4] - 2026-07-24