[libc++][docs] Update to refer to P3355R2 (#167267)

Per cplusplus/draft#7505, LWG approved P3355R2
and the differences between P3355R1 is subsequently applied. So it seems
better to refer to P3355R2.

Author: frederick-vs-ja

libcxx/docs/Status/Cxx2cPapers.csv

@@ -81,7 +81,7 @@
 "`P3379R0 <https://wg21.link/P3379R0>`__","Constrain ``std::expected`` equality operators","2024-11 (Wrocław)","|Complete|","21","`#118135 <https://github.com/llvm/llvm-project/issues/118135>`__",""
 "`P2862R1 <https://wg21.link/P2862R1>`__","``text_encoding::name()`` should never return null values","2024-11 (Wrocław)","","","`#118371 <https://github.com/llvm/llvm-project/issues/118371>`__",""
 "`P2897R7 <https://wg21.link/P2897R7>`__","``aligned_accessor``: An ``mdspan`` accessor expressing pointer over-alignment","2024-11 (Wrocław)","|Complete|","21","`#118372 <https://github.com/llvm/llvm-project/issues/118372>`__",""
-"`P3355R1 <https://wg21.link/P3355R1>`__","Fix ``submdspan`` for C++26","2024-11 (Wrocław)","","","`#118373 <https://github.com/llvm/llvm-project/issues/118373>`__",""
+"`P3355R2 <https://wg21.link/P3355R2>`__","Fix ``submdspan`` for C++26","2024-11 (Wrocław)","","","`#118373 <https://github.com/llvm/llvm-project/issues/118373>`__",""
 "`P3222R0 <https://wg21.link/P3222R0>`__","Fix C++26 by adding transposed special cases for P2642 layouts","2024-11 (Wrocław)","","","`#118374 <https://github.com/llvm/llvm-project/issues/118374>`__",""
 "`P3050R2 <https://wg21.link/P3050R2>`__","Fix C++26 by optimizing ``linalg::conjugated`` for noncomplex value types","2024-11 (Wrocław)","","","`#118375 <https://github.com/llvm/llvm-project/issues/118375>`__",""
 "`P3396R1 <https://wg21.link/P3396R1>`__","``std::execution`` wording fixes","2024-11 (Wrocław)","","","`#118376 <https://github.com/llvm/llvm-project/issues/118376>`__",""