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

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

NOKEYCHECK=True
GitOrigin-RevId: bfbd73f87d7b2c1140b43192cea6b7fbbfc35cd0
diff --git a/include/optional b/include/optional
index e4f3938..b6a464f 100644
--- a/include/optional
+++ b/include/optional
@@ -146,8 +146,8 @@
 
 */
 
-#include <__config>
 #include <__availability>
+#include <__config>
 #include <__debug>
 #include <__functional_base>
 #include <compare>