[clang] Add release notes for resolving issue #117960

Author: thebrandre

clang/docs/ReleaseNotes.rst

@@ -938,6 +938,9 @@ Miscellaneous Clang Crashes Fixed
 - Fixed internal assertion firing when a declaration in the implicit global
   module is found through ADL. (GH#109879)
 
+- Fixed a crash when an unscoped enumeration declared by an opaque-enum-declaration within a class template
+  with a dependent underlying type is subject to integral promotion. (GH#117960)
+
 OpenACC Specific Changes
 ------------------------