[func.wrap.badcall] Add missing \itemdecl for what() (#3629)

Author: timsong-cpp

source/utilities.tex

@@ -15381,6 +15381,10 @@
 \end{codeblock}
 
 \indexlibrarymember{what}{bad_function_call}%
+\begin{itemdecl}
+const char* what() const noexcept override;
+\end{itemdecl}
+
 \begin{itemdescr}
 \pnum
 \returns