chore(combobox-web): document multiselect Backspace select-all clearing fix

Author: samuelreichert

packages/pluggableWidgets/combobox-web/CHANGELOG.md

@@ -6,6 +6,10 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 
 ## [Unreleased]
 
+### Fixed
+
+- We fixed an issue where selecting all of the typed text in a multi-select combobox and pressing Backspace did not permanently clear it, so the text reappeared after clicking away and back into the combobox.
+
 ## [2.9.0] - 2026-07-24
 
 ### Fixed