docs: add changelog entry for format_voter_id fix

Author: gaoflow

CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Fixed
+
+- `format_voter_id` [#742](https://github.com/brazilian-utils/python/pull/742)
+
 ## [2.4.0] - 2026-04-20
 
 ### Added