Add gh-173 to changelog

Author: ndgrigorian

CHANGELOG.md

@@ -8,6 +8,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Removed
 * Dropped support for Python 3.9 [gh-118](https://github.com/IntelPython/mkl-service/pull/118)
+* Dropped support for `"ssse3"`, `"sse4_1"`, `"avx"`, `"avx512_mic"`, `"avx512_mic,strict"`, and `"avx512_mic_e1"` cbwr branches [gh-173](https://github.com/IntelPython/mkl-service/pull/173)
 
 ## [2.6.1] (11/25/2025)