gnome-text-editor: don't check 'System' tab in About
    
    In 43-alpha it's gone, the replacement is Troubleshooting ->
    Debugging Information. But it would be a pain to write two
    forks in the code for handling both cases, and there's a ton
    more stuff in the new-style About dialog that we're not
    checking either. I don't think we really need to click on all
    of it, and this bit of it isn't super important. So on the
    whole I'd rather just keep things simple and drop this check.
    
    Signed-off-by: Adam Williamson <awilliam@redhat.com>