fixup: formatting of S

Author: jensmaurer

source/classes.tex

@@ -1233,12 +1233,12 @@
 as applied to find \tcode{M}'s corresponding constructor
 does not result in a usable candidate\iref{over.match.general}, or
 
-\item any potentially constructed subobject \tcode{S} has
+\item any potentially constructed subobject $S$ has
 class type \tcode{M} (or possibly multidimensional array thereof),
 \tcode{M} has
 a destructor that is deleted or inaccessible from the defaulted default
 constructor, and
-either \tcode{S} is non-variant or \tcode{S} has a default member initializer.
+either $S$ is non-variant or $S$ has a default member initializer.
 \end{itemize}
 
 \pnum