[libc++] Mark LWG3404 as implemented

LWG3404 was implemented along with subrange.

Closes llvm#104282

Author: ldionne

libcxx/docs/Status/Cxx20Issues.csv

@@ -218,7 +218,7 @@
 "`LWG3269 <https://wg21.link/LWG3269>`__","Parse manipulators do not specify the result of the extraction from stream","2020-02 (Prague)","","","|chrono|"
 "`LWG3270 <https://wg21.link/LWG3270>`__","Parsing and formatting ``%j``\  with ``duration``\ s","2020-02 (Prague)","|Partial|","","|chrono| |format|"
 "`LWG3280 <https://wg21.link/LWG3280>`__","View converting constructors can cause constraint recursion and are unneeded","2020-02 (Prague)","|Complete|","15.0","|ranges|"
-"`LWG3281 <https://wg21.link/LWG3281>`__","Conversion from ``*pair-like*``\  types to ``subrange``\  is a silent semantic promotion","2020-02 (Prague)","|Complete|","15.0","|ranges|"
+"`LWG3281 <https://wg21.link/LWG3281>`__","Conversion from ``*pair-like*``\  types to ``subrange``\  is a silent semantic promotion","2020-02 (Prague)","|Complete|","13.0","|ranges|"
 "`LWG3282 <https://wg21.link/LWG3282>`__","``subrange``\  converting constructor should disallow derived to base conversions","2020-02 (Prague)","|Complete|","15.0","|ranges|"
 "`LWG3284 <https://wg21.link/LWG3284>`__","``random_access_iterator``\  semantic constraints accidentally promote difference type using unary negate","2020-02 (Prague)","|Nothing To Do|","","|ranges|"
 "`LWG3285 <https://wg21.link/LWG3285>`__","The type of a customization point object shall satisfy ``semiregular``\ ","2020-02 (Prague)","|Nothing To Do|","","|ranges|"

libcxx/docs/Status/Cxx23Issues.csv

@@ -20,7 +20,7 @@
 "`LWG3171 <https://wg21.link/LWG3171>`__","LWG2989 breaks ``directory_entry`` stream insertion","2020-11 (Virtual)","|Complete|","14.0",""
 "`LWG3306 <https://wg21.link/LWG3306>`__","``ranges::advance`` violates its preconditions","2020-11 (Virtual)","|Complete|","14.0","|ranges|"
 "`LWG3403 <https://wg21.link/LWG3403>`__","Domain of ``ranges::ssize(E)`` doesn't ``match ranges::size(E)``","2020-11 (Virtual)","","","|ranges|"
-"`LWG3404 <https://wg21.link/LWG3404>`__","Finish removing subrange's conversions from pair-like","2020-11 (Virtual)","","","|ranges|"
+"`LWG3404 <https://wg21.link/LWG3404>`__","Finish removing subrange's conversions from pair-like","2020-11 (Virtual)","|Complete|","13.0","|ranges|"
 "`LWG3405 <https://wg21.link/LWG3405>`__","``common_view``'s converting constructor is bad, too","2020-11 (Virtual)","|Complete|","14.0","|ranges|"
 "`LWG3406 <https://wg21.link/LWG3406>`__","``elements_view::begin()`` and ``elements_view::end()`` have incompatible constraints","2020-11 (Virtual)","|Complete|","16.0","|ranges|"
 "`LWG3419 <https://wg21.link/LWG3419>`__","[algorithms.requirements]/15 doesn't reserve as many rights as it intends to","2020-11 (Virtual)","|Nothing To Do|","",""