[mdspan.submdspan.extents] Format equations as math (#6530)

Author: Eelis

source/containers.tex

@@ -21757,8 +21757,8 @@
 \item
 if $S_k$ is a specialization of \tcode{strided_slice}
   \begin{itemize}
-  \item $\tcode{$s_k$.extent = 0}$, or
-  \item $\tcode{$s_k$.stride > 0}$
+  \item $\tcode{$s_k$.extent} = 0$, or
+  \item $\tcode{$s_k$.stride} > 0$
   \end{itemize}
 \item
 $0 \le \tcode{\exposid{first_}<IndexType, $k$>(slices...)}$