qt: Remove client name from debug window

Remove the client name from the debug window in the GUI. It is already
part of the user agent, so adding it separately doesn't add anything.

src/qt/clientmodel.cpp

@@ -191,11 +191,6 @@ bool ClientModel::isReleaseVersion() const
     return CLIENT_VERSION_IS_RELEASE;
 }
 
-QString ClientModel::clientName() const
-{
-    return QString::fromStdString(CLIENT_NAME);
-}
-
 QString ClientModel::formatClientStartupTime() const
 {
     return QDateTime::fromTime_t(nClientStartupTime).toString();