[Clang] Add missing words to ReleaseNotes.rst

Author: cor3ntin

clang/docs/ReleaseNotes.rst

@@ -95,6 +95,7 @@ C++23 Feature Support
   implemented (`CWG2553 <https://wg21.link/CWG2553>`_, `CWG2554 <https://wg21.link/CWG2554>`_,
   `CWG2653 <https://wg21.link/CWG2653>`_, `CWG2687 <https://wg21.link/CWG2687>`_). Because the
   support for this feature is still experimental, the feature test macro ``__cpp_explicit_this_parameter``
+  was not set in this version.
 
 C++2c Feature Support
 ^^^^^^^^^^^^^^^^^^^^^