[libc++] NFCI: Remove __functional/search.h

The __search helper function was once split into __functional for circular
dependency reasons, however this is not an issue anymore now that we have
finer grained headers.

NOKEYCHECK=True
GitOrigin-RevId: d03aa7d6b66fd741db2d937c18a6c6675037b888
diff --git a/include/functional b/include/functional
index 2b2dcd2..976b945 100644
--- a/include/functional
+++ b/include/functional
@@ -487,11 +487,11 @@
 
 */
 
+#include <__algorithm/search.h>
 #include <__config>
 #include <__debug>
 #include <__functional_base>
 #include <__functional/hash.h>
-#include <__functional/search.h>
 #include <__functional/unary_function.h>
 #include <__functional/unwrap_ref.h>
 #include <__utility/forward.h>