[bitcoin/bitcoin] Use new Qt5 connect syntax (#13529)

promag commented on this pull request.

>
// start with displaying the «out of sync» warnings
showOutOfSyncWarning(true);
— connect(ui->labelWalletStatus, SIGNAL(clicked()), this, SLOT(handleOutOfSyncWarningClicks()));
— connect(ui->labelTransactionsStatus, SIGNAL(clicked()), this, SLOT(handleOutOfSyncWarningClicks()));
+ connect(ui->labelWalletStatus, &QPushButton::clicked, this, &OverviewPage::handleOutOfSyncWarningClicks);
+ connect(ui->labelWalletStatus, &QPushButton::clicked, this, &OverviewPage::handleOutOfSyncWarningClicks);

Removed.