[simd.permute.memory] Rename 'simd' to 'vec' in subclause title

Fixes NB US 184-291 (C++26 CD).

Author: jensmaurer

source/numerics.tex

@@ -18954,7 +18954,7 @@
 for all $i$ in the range \range{0}{V::size()}.
 \end{itemdescr}
 
-\rSec3[simd.permute.memory]{\tcode{simd} memory permute}
+\rSec3[simd.permute.memory]{\tcode{vec} memory permute}
 
 \indexlibrarymember{unchecked_gather_from}{simd}
 \begin{itemdecl}