Remove a Qt 5 to-do comment that will not be addressed.

Task-number: QTBUG-25102
Change-Id: I3fe1878adcf17cb95209df271d062e126e32a8fd
Reviewed-by: Lars Knoll <lars.knoll@nokia.com>

src/widgets/widgets/qtabbar.cpp

@@ -1299,7 +1299,6 @@ static QString computeElidedText(Qt::TextElideMode mode, const QString &text)
 QSize QTabBarPrivate::minimumTabSizeHint(int index)
 {
     Q_Q(QTabBar);
-    // ### Qt 5: make this a protected virtual function in QTabBar
     Tab &tab = tabList[index];
     QString oldText = tab.text;
     tab.text = computeElidedText(elideMode, oldText);