[libc++] Restore order of includes on Windows to unbreak the build

As reported in [1], it looks like the Windows headers are picky about
the order in which they are included, and the clang-format change broke
the build by reordering the headers.

[1]: #74334 (comment)

Author: ldionne

libcxx/src/support/win32/thread_win32.cpp

@@ -11,9 +11,9 @@
 
 #define NOMINMAX
 #define WIN32_LEAN_AND_MEAN
-#include <fibersapi.h>
-#include <process.h>
 #include <windows.h>
+#include <process.h>
+#include <fibersapi.h>
 
 _LIBCPP_BEGIN_NAMESPACE_STD