QAbstractSpinBox: respond to QEvent::LocaleChange

Add a branch for QEvent::LocaleChange to the QAbstractSpinBox::event()
handler to call updateEdit(). This will update the edit in case the
locale's number features changed (decimal separator etc.).

Task-number: QTBUG-65315
Change-Id: I9015b3a5bbe8e7b80f7bafa13f0f431507bc4cf7
Reviewed-by: Christian Ehrlicher <ch.ehrlicher@gmx.de>
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@qt.io>

src/widgets/widgets/qabstractspinbox.cpp

@@ -828,6 +828,9 @@ void QAbstractSpinBox::changeEvent(QEvent *event)
             d->reset();
             d->updateEditFieldGeometry();
             break;
+        case QEvent::LocaleChange:
+            d->updateEdit();
+            break;
         case QEvent::EnabledChange:
             if (!isEnabled()) {
                 d->reset();