Build: fix variable order initialization error

fatal error: field 'Action' will be initialized after field 'Validator' [-Wreorder]

(cherry picked from commit 71e7394b74)

src/server/game/Movement/MotionMaster.h

@@ -96,8 +96,8 @@ class MotionMasterDelayedAction
 
         void Resolve() { if (Validator()) Action(); }
 
-        std::function<bool()> Validator;
         std::function<void()> Action;
+        std::function<bool()> Validator;
         uint8 Type;
 };