Move the inclusion of optional header file in UserDefaults.h

Author: nivi-apple

src/platform/Darwin/UserDefaults.h

@@ -16,6 +16,8 @@
 
 #pragma once
 
+#include <optional>
+
 namespace chip {
 namespace Platform {
 

src/platform/Darwin/UserDefaults.mm

@@ -19,7 +19,6 @@
 
 #include <lib/support/SafeInt.h>
 #include <lib/support/logging/CHIPLogging.h>
-#include <optional>
 
 static NSString * const kUserDefaultDomain = @"org.csa-iot.matter.darwin";
 static NSString * const kSRPTimeoutInMsecsUserDefaultKey = @"SRPTimeoutInMSecsOverride";