[libc++] Granularize <type_traits> includes in <compare>

Reviewed By: Mordante, #libc

Spies: libcxx-commits

Differential Revision: https://reviews.llvm.org/D140480

NOKEYCHECK=True
GitOrigin-RevId: e0a66116fcccd59d12485810f5311efafa134ea5
diff --git a/include/condition_variable b/include/condition_variable
index 6b4d506..f13df1c 100644
--- a/include/condition_variable
+++ b/include/condition_variable
@@ -270,6 +270,7 @@
 
 #if !defined(_LIBCPP_REMOVE_TRANSITIVE_INCLUDES) && _LIBCPP_STD_VER <= 20
 #  include <concepts>
+#  include <type_traits>
 #endif
 
 #endif // _LIBCPP_CONDITION_VARIABLE