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

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

NOKEYCHECK=True
GitOrigin-RevId: bfbd73f87d7b2c1140b43192cea6b7fbbfc35cd0
diff --git a/include/shared_mutex b/include/shared_mutex
index 72a0ffa..8205c3e 100644
--- a/include/shared_mutex
+++ b/include/shared_mutex
@@ -122,8 +122,8 @@
 
 */
 
-#include <__config>
 #include <__availability>
+#include <__config>
 #include <version>
 
 _LIBCPP_PUSH_MACROS