[libc++] [C++2b] [P1048] Add is_scoped_enum and is_scoped_enum_v.

* https://wg21.link/p1048

Reviewed By: ldionne, #libc

Differential Revision: https://reviews.llvm.org/D94409

GitOrigin-RevId: 1f1250151f222ba391d05dcc173f4b6c65d05ca2
diff --git a/docs/FeatureTestMacroTable.rst b/docs/FeatureTestMacroTable.rst
index 99fb4e7..8221bbe 100644
--- a/docs/FeatureTestMacroTable.rst
+++ b/docs/FeatureTestMacroTable.rst
@@ -292,7 +292,7 @@
     ------------------------------------------------- -----------------
     **C++ 2b**
     -------------------------------------------------------------------
-    ``__cpp_lib_is_scoped_enum``                      *unimplemented*
+    ``__cpp_lib_is_scoped_enum``                      ``202011L``
     ------------------------------------------------- -----------------
     ``__cpp_lib_stacktrace``                          *unimplemented*
     ------------------------------------------------- -----------------