Backport 0.4.3 changelog entry from maintenance/0.4.x

Record the 0.4.3 release on main and move the gh-226 entry from the
unreleased [dev] section into the released [0.4.3] section, matching the
finalized changelog on the maintenance/0.4.x branch.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: antonwolfy

CHANGELOG.md

@@ -11,10 +11,14 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Changed
 * Removed `numpy-base` dependency and `USE_NUMPY_BASE` environment variable from conda recipe [gh-200](https://github.com/IntelPython/mkl_umath/pull/200)
-* Updated `mkl_umath` patching to work with changes to NumPy Cython API present in NumPy 2.5 [gh-226](https://github.com/IntelPython/mkl_umath/pull/226)
 
 ### Fixed
 
+## [0.4.3] - 2026-06-30
+
+### Changed
+* Updated `mkl_umath` patching to work with changes to NumPy Cython API present in NumPy 2.5 [gh-226](https://github.com/IntelPython/mkl_umath/pull/226)
+
 ## [0.4.2] - 2026-05-28
 
 ### Added