libstdc++: Fix doxygen comment for std::out_ptr [PR124024] libstdc++-v3/ChangeLog: PR libstdc++/124024 * include/bits/out_ptr.h (out_ptr): Fix doxygen comment to refer to the right function. (inout_ptr): Improve markup in doxygen comment. (cherry picked from commit a53eaa269058c0e382178505bb2b414132d04ded)