VcsBase: Adjusting incompatible signal/slot

This is a fix for

QObject::connect: No such slot
VcsBase::VcsBaseOutputWindow::appendCommand(QString,QString,QStringList)
in command.cpp:323

Change-Id: I6c68456081c323ec1d4bf67f13982c71c25ade3a
Reviewed-by: Orgad Shaneh <orgads@gmail.com>