[libc++] Alphabetize and include-what-you-use. NFCI.

Differential Revision: https://reviews.llvm.org/D102781

NOKEYCHECK=True
GitOrigin-RevId: bfbd73f87d7b2c1140b43192cea6b7fbbfc35cd0
diff --git a/include/__tree b/include/__tree
index 70f3a27..b599a04 100644
--- a/include/__tree
+++ b/include/__tree
@@ -11,10 +11,10 @@
 #define _LIBCPP___TREE
 
 #include <__config>
+#include <algorithm>
 #include <iterator>
 #include <memory>
 #include <stdexcept>
-#include <algorithm>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header