[linalg.transp.transposed] Add missing "a.mapping()".

It seems to have been omitted by oversight, but is clearly intended.

Author: tkoeppe

source/numerics.tex

@@ -13127,7 +13127,7 @@
 otherwise,
 \begin{codeblock}
 R(a.data_handle(), ReturnMapping(@\exposid{transpose-extents}@(a.mapping().extents()),
-  a.stride(0)), a.accessor())
+  a.mapping().stride(0)), a.accessor())
 \end{codeblock}
 if \tcode{Layout} is \tcode{layout_right_padded<PaddingValue>}
 for some \tcode{size_t} value \tcode{PaddingValue};