[mdspan.layout.left.obs] Add missing noexcept (cplusplus#7831)

Author: hewillk

source/containers.tex

@@ -22210,7 +22210,7 @@
 
 \indexlibrarymember{stride}{layout_left::mapping}%
 \begin{itemdecl}
-constexpr index_type stride(rank_type i) const;
+constexpr index_type stride(rank_type i) const noexcept;
 \end{itemdecl}
 
 \begin{itemdescr}