[Review] Add line in the Release notes

Author: jmmartinez

clang/docs/ReleaseNotes.rst

@@ -165,6 +165,7 @@ Non-comprehensive list of changes in this release
 
 - Support parsing the `cc` operand modifier and alias it to the `c` modifier (#GH127719).
 - Added `__builtin_elementwise_exp10`.
+- For AMDPGU targets, added `__builtin_v_cvt_off_f32_i4` that maps to the `v_cvt_off_f32_i4` instruction.
 
 New Compiler Flags
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