bpo-44340: Update whatsnews for ThinLTO (GH-28229)

Co-authored-by: Łukasz Langa <[email protected]>

Author: corona10

Doc/whatsnew/3.11.rst

@@ -299,6 +299,9 @@ CPython bytecode changes
 Build Changes
 =============
 
+* CPython can now be built with the ThinLTO option via ``--with-lto=thin``.
+  (Contributed by Dong-hee Na and Brett Holman in :issue:`44340`.)
+
 
 Deprecated
 ==========