[clang] [NFC][Clang][Headers] Update refs to ACLE in comments (PR #78305)

[James Westwood via cfe-commits]

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@@ -540,7 +545,7 @@ __usub16(uint16x2_t __a, uint16x2_t __b) {
 }
 #endif
 
-/* 9.5.10 Parallel 16-bit multiplications */
+/* 8.5.10 Parallel 16-bit multiplications */
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jwestwood921 wrote:

Nit pick: The ACLE document has 'multiplication', instead of 'multiplications'.

https://github.com/llvm/llvm-project/pull/78305