[GUI] keycode.h: Qt < 5.6 compat

QHash is included already before anyway...

Author: adriweb

gui/qt/keypad/keycode.h

@@ -1,7 +1,7 @@
 #ifndef KEYCODE_H
 #define KEYCODE_H
 
-#include <QtCore/QHashFunctions>
+#include <QtCore/QHash>
 
 struct KeyCode {
     KeyCode() : mCode(~0) {}