message: qt: drop workaround for which was fixed in Qt 5.5.0
  Fixes
diff: @@ -152,7 +152,6 @@ OverviewPage::OverviewPage(const PlatformStyle *platformStyle, QWidget *parent)
  // use a SingleColorIcon for the "out of sync warning" icon
  QIcon icon = QIcon(":/icons/warning");
  - icon.addPixmap(icon.pixmap(QSize(64,64), QIcon::Normal), QIcon::Disabled); // also set the disabled icon because we are using a disabled QPushButton to work around missing HiDPI support of QLabel (https://bugreports.qt.io/browse/QTBUG-42503)
  ui->labelTransactionsStatus->setIcon(icon);
  ui->labelWalletStatus->setIcon(icon);
  