Right click on the tab and select Maximise. A Restore button will appear near the Command Finder to revert back.
I can't find anything in the Customer Defaults. There is a line in the syslog that states 'Multiple Displayed Parts capability is enabled' which suggests that you could disable it.
The question I am wondering about here is why? How much space are the tabs really taking up in the context of being able to have multiple displayed parts? With the size of monitors today I do not really see that as a big issue. Can you please share some images of your screen or what you are trying to accomplish by this request.
In my view the advantage of having Multiple Display Parts (MDP) far outways the ability to switch off the tabs permanently. Increased graphics performance switching between parts is instantaneous as opposed to the old switch display parts. As someone else said its simple to maximise the window to remove the tabs too. I really do not understand how a small group of tabs are causing pain unless you are working on a very small screen.