[expr.alignof] Use "declared" for std::size_t

Author: frederick-vs-ja

source/expressions.tex

@@ -5029,7 +5029,7 @@
 \begin{note}
 An \keyword{alignof} expression
 is an integral constant expression\iref{expr.const}.
-The type \tcode{std::size_t} is defined in the standard header
+The \grammarterm{typedef-name} \tcode{std::size_t} is declared in the standard header
 \libheader{cstddef}\iref{cstddef.syn,support.types.layout}.
 \end{note}