Improve sender field in mail notifications

Problem statement: user sees its email address in email notification,
while it is better to have sender field app-personalized, like it did
in Nextcloud: they send notifications from user's email address and
add alias 'Nextcloud' to it.

This patch adds alias 'qBittorrent' to qBittorrent email notifications,
so user sees more user-friendly email notification.

PR #17374.

src/app/application.cpp

@@ -476,7 +476,7 @@ void Application::sendNotificationEmail(const BitTorrent::Torrent *torrent)
     auto *smtp = new Net::Smtp(this);
     smtp->sendMail(pref->getMailNotificationSender(),
                      pref->getMailNotificationEmail(),
-                     tr("[qBittorrent] '%1' has finished downloading").arg(torrent->name()),
+                     tr("Torrent \"%1\" has finished downloading").arg(torrent->name()),
                      content);
 }