[mdspan.layout.leftpad.cons] Add missing \exposid around "index-cast"

Author: eisenwave

source/containers.tex

@@ -23196,7 +23196,7 @@
 \item
 \tcode{pad} is representable as a value of type \tcode{index_type}.
 \item
-\tcode{extents_type::index-cast(pad)} is greater than zero.
+\tcode{extents_type::\exposid{index-cast}(pad)} is greater than zero.
 \item
 If \exposid{rank_} is greater than one,
 then \tcode{\exposid{LEAST-MULTIPLE-AT-LEAST}(pad, ext.extent(0))}