[Clang][Docs] Clarify release notes. NFC.

Author: dtcxzyw

clang/docs/ReleaseNotes.rst

@@ -42,11 +42,12 @@ Potentially Breaking Changes
 C/C++ Language Potentially Breaking Changes
 -------------------------------------------
 
-- Some old-style offsetof idioms like ``((int)(&(((struct S *)0)->field)))`` are treated
-  as UB. To avoid breaking existing code, ``inbounds`` flags will not be set for such patterns.
-  However, it is still highly recommended to use the UB-free macro ``offsetof`` or clang builtin
-  function ``__builtin_offsetof``. It is also possible to use ``-fwrapv-pointer`` or 
-  ``-fno-delete-null-pointer-checks`` to make this behavior well-defined. (#GH130734, #GH130742)
+- New LLVM optimizations have been implemented that optimize pointer arithmetic on
+  null pointers more aggressively.  As part of this, clang has implemented a special
+  case for old-style offsetof idioms like ``((int)(&(((struct S *)0)->field)))``, to
+  ensure they are not caught by these optimizations.  It is also possible to use
+  ``-fwrapv-pointer`` or   ``-fno-delete-null-pointer-checks`` to make pointer arithmetic
+  on null pointers well-defined. (#GH130734, #GH130742)
 
 C++ Specific Potentially Breaking Changes
 -----------------------------------------