Add a release note.

Author: katzdm

clang/docs/ReleaseNotes.rst

@@ -217,6 +217,8 @@ Bug Fixes to C++ Support
 - Clang now preserves the unexpanded flag in a lambda transform used for pack expansion. (#GH56852), (#GH85667),
   (#GH99877).
 - Fixed a bug when diagnosing ambiguous explicit specializations of constrained member functions.
+- Fixed an assertion failure when selecting a function from an overload set that includes a 
+  specialization of a conversion function template.
 
 Bug Fixes to AST Handling
 ^^^^^^^^^^^^^^^^^^^^^^^^^