Update release notes

Author: SLTozer

llvm/docs/ReleaseNotes.rst

@@ -171,10 +171,11 @@ Changes to the Debug Info
 ---------------------------------
 
 * LLVM has switched from using debug intrinsics internally to using debug
-  records. This should happen transparently when using the DIBuilder to
-  construct debug variable information, but will require changes for any code
-  that interacts with debug intrinsics directly; for more information, see the
-  `migration docs <https://llvm.org/docs/RemoveDIsDebugInfo.html>`_.
+  records by default. This should happen transparently when using the DIBuilder
+  to construct debug variable information, but will require changes for any code
+  that interacts with debug intrinsics directly. Debug intrinsics will only be
+  supported on a best-effort basis from here onwards; for more information, see
+  the `migration docs <https://llvm.org/docs/RemoveDIsDebugInfo.html>`_.
 
 Changes to the LLVM tools
 ---------------------------------