platform: correct case for WinSDK module (NFC)

This adjusts the case so that it can build on case sensitive file
systems (e.g. ext4).

Author: compnerd

stdlib/public/Platform/winsdk.modulemap

@@ -19,7 +19,7 @@ module WinSDK [system] [extern_c] {
 
   module core {
     module acl {
-      header "aclapi.h"
+      header "AclAPI.h"
       export *
     }