As with other themes, those lines (or similar) are in tiki-top_bar.tpl — templates/tikipedia/tiki-top_bar.tpl, specifically.
I was successful in removing
by using display : none; in a few instances, which makes my left column navigation nice and tight, so I can focus on my structure modules.
But for the life of me I can't find how to turn off that Tiki / CMS text line.
Is it part of Site Title?
I do need the top menus Edit Remove Rename, etc., so I don't want to lose those.
I'd recommend getting a text editor that can search for a text string in a directory of files. Then you can enter "Tiki CMS/Groupware" or whatever in a search of the Tikipedia theme directories and it'll turn up the file and show you the line, which you can then edit. For Windows, TextPad is a good shareware editor that can do this, and I'm sure there are a lot of others also for other OSs.