chore: update release changelog description

Author: Qbandev

CHANGELOG.md

@@ -9,9 +9,13 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [5.1.1]
 
-### Uncategorized
+### Fixed
 
-- fix(INFRA-3081): implement duplicate detection for all commit types ([#254](https://github.com/MetaMask/auto-changelog/pull/254))
+- Fix duplicate changelog entries ([#254](https://github.com/MetaMask/auto-changelog/pull/254))
+  - PR-based commits: Deduplication now checks if PR number already exists in changelog
+  - Direct commits (no PR number): Deduplication now checks if exact description text already exists in changelog
+  - Squash merges: Feature branch commits are skipped when a corresponding merge commit with the same description exists
+  - Merge commits: Now properly categorized using PR content instead of the generic merge subject
 
 ## [5.1.0]