[FOLD] add release note

Author: sdkrystian

clang/docs/ReleaseNotes.rst

@@ -114,6 +114,9 @@ Improvements to Clang's diagnostics
 - Clang now applies syntax highlighting to the code snippets it
   prints.
 
+- Clang now diagnoses use of the ``template`` keyword after declarative nested name specifiers.
+
+
 Improvements to Clang's time-trace
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