Pretty sure you can't permanently remove them. However, if you deselect Toolbox and Enterprise PDM under the 'Add-ins' menu, they'll go away. But, you'll also be turning off those add-ins. You could also click on the pin to the right of 'Help' so that the whole menu bar collapses when you don't need it.
Out of curiosity, why add toolbars? Between the command manager, and the 'S' key, you can get away from toolbars almost completely.