Add release note

Author: AaronBallman

clang/docs/ReleaseNotes.rst

@@ -620,6 +620,14 @@ Improvements to Clang's diagnostics
 
 - Improved the FixIts for unused lambda captures.
 
+- Delayed typo correction was removed from the compiler; immediate typo
+  correction behavior remains the same. Delayed typo correction facilities were
+  fragile and unmaintained, and the removal closed the following issues:
+  #GH142457, #GH139913, #GH138850, #GH137867, #GH137860, #GH107840, #GH93308,
+  #GH69470, #GH59391, #GH58172, #GH46215, #GH45915, #GH45891, #GH44490,
+  #GH36703, #GH32903, #GH23312, #GH69874.
+
+
 Improvements to Clang's time-trace
 ----------------------------------