[libc++][NFC] Remove unused include in <compare>.

`<type_traits>` was included in the first iteration of `<compare>` when
it was created as a monolithic header, then never removed. Removing it
now is a beneficial no-op since it is not guaranteed by the standard
and is already included by all of its subheaders.

Reviewed By: cjdb, #libc, Quuxplusone

Differential Revision: https://reviews.llvm.org/D107801

diff --git a/libcxx/include/compare b/libcxx/include/compare
index f681454..4c11f13 100644 (file)
--- a/libcxx/include/compare
+++ b/libcxx/include/compare
@@ -130,7 +130,6 @@ namespace std {
 #include <__compare/compare_three_way_result.h>
 #include <__compare/ordering.h>
 #include <__config>
-#include <type_traits>
 
 #ifndef _LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER
 #pragma GCC system_header