[libc++] [NFC] Mark P0858R0 as implemented

P0858R0 seems to be implemented. D93830 sets `__cpp_lib_string_view` and D80452 sets `__cpp_lib_array_constexpr`.

Reviewed By: Quuxplusone, Mordante, ldionne, #libc

Spies: libcxx-commits

Differential Revision: https://reviews.llvm.org/D114344

GitOrigin-RevId: 04a6dc06a07b9eb89834a4ae80f56749de7474e7
diff --git a/docs/Status/Cxx20Papers.csv b/docs/Status/Cxx20Papers.csv
index 8d824fd..d2ce8dd 100644
--- a/docs/Status/Cxx20Papers.csv
+++ b/docs/Status/Cxx20Papers.csv
@@ -22,7 +22,7 @@
 "`P0753R2 <https://wg21.link/P0753R2>`__","LWG","Manipulators for C++ Synchronized Buffered Ostream","Jacksonville","",""
 "`P0754R2 <https://wg21.link/P0754R2>`__","LWG","<version>","Jacksonville","|Complete|","7.0"
 "`P0809R0 <https://wg21.link/P0809R0>`__","LWG","Comparing Unordered Containers","Jacksonville","|Nothing To Do|",""
-"`P0858R0 <https://wg21.link/P0858R0>`__","LWG","Constexpr iterator requirements","Jacksonville","",""
+"`P0858R0 <https://wg21.link/P0858R0>`__","LWG","Constexpr iterator requirements","Jacksonville","|Complete|","12.0"
 "`P0905R1 <https://wg21.link/P0905R1>`__","CWG","Symmetry for spaceship","Jacksonville","",""
 "`P0966R1 <https://wg21.link/P0966R1>`__","LWG","``string::reserve``\  Should Not Shrink","Jacksonville","|Complete| [#note-P0966]_","12.0"
 "","","","","",""