QCoreApplicationPrivate: make the type member 8 bits

So it packs better with the booleans around it.

Pick-to: 6.9
Change-Id: I330164b99fcbbf9e9629fffd52bcbb38bec4ac0e
Reviewed-by: Ivan Solovev <ivan.solovev@qt.io>

src/corelib/kernel/qcoreapplication_p.h

@@ -48,7 +48,7 @@ class Q_CORE_EXPORT QCoreApplicationPrivate
     Q_DECLARE_PUBLIC(QCoreApplication)
 
 public:
-    enum Type {
+    enum Type : quint8 {
         Tty,
         Gui
     };