Update clang/docs/ReleaseNotes.rst

Co-authored-by: Chris B <[email protected]>

Author: spall

clang/docs/ReleaseNotes.rst

@@ -193,8 +193,8 @@ Improvements to Clang's diagnostics
   under the subgroup ``-Wunsafe-buffer-usage-in-libc-call``.
 - Diagnostics on chained comparisons (``a < b < c``) are now an error by default. This can be disabled with
   ``-Wno-error=parentheses``.
-- Adds a diagnostic for out of bounds vector accesses; Errors by default for compile time statically
-  provable out of bounds vector accesses.
+- Adds an error diagnostic for out of bounds vector accesses; produces an error
+  for compile time statically provable out of bounds vector accesses.
 
 Improvements to Clang's time-trace
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