[cstdarg.syn] Update to refer to C23 6.5.3.3

... due to new sections added after WG14 N3220

Author: frederick-vs-ja

source/support.tex

@@ -6410,7 +6410,7 @@
 standard library header \libheader{stdarg.h}, with the following changes:
 \begin{itemize}
 \item
-In lieu of the default argument promotions specified in \IsoC{} 6.5.2.2,
+In lieu of the default argument promotions specified in \IsoC{} 6.5.3.3,
 the definition in~\ref{expr.call} applies.
 \item
 The preprocessing tokens