[libc++] Implement P1328R1 constexpr std::type_info::operator==

Differential Revision: https://reviews.llvm.org/D143447

NOKEYCHECK=True
GitOrigin-RevId: 16a1c851713a5825daed8ea4a887078a63488562
diff --git a/docs/FeatureTestMacroTable.rst b/docs/FeatureTestMacroTable.rst
index b46fc8c..df4dfc4 100644
--- a/docs/FeatureTestMacroTable.rst
+++ b/docs/FeatureTestMacroTable.rst
@@ -316,7 +316,7 @@
     ------------------------------------------------- -----------------
     ``__cpp_lib_constexpr_memory``                    ``202202L``
     ------------------------------------------------- -----------------
-    ``__cpp_lib_constexpr_typeinfo``                  *unimplemented*
+    ``__cpp_lib_constexpr_typeinfo``                  ``202106L``
     ------------------------------------------------- -----------------
     ``__cpp_lib_expected``                            ``202202L``
     ------------------------------------------------- -----------------