The Mendix Profile menu widget ('platformbar') is positioned in the Navigation Layouts.
You could open the Navigation Layouts in your project and remove the Mendix Profile menu widget from the relevant Layouts.
Ps You could also replace the Navigation Layouts modules by the one from the App store, if you do not use the App Cloud Services module in your project. This module does not contain the Mendix Profile Menu widget & Mendix AppSwitcher widgets in the Navigation Layouts.
* https://appstore.home.mendix.com/link/app/23513/Mendix/Administration-module (Navigation Layouts modules has dependency on this module)
(Note: there's also a Navigation Layouts module in the App store with dependency on App Cloud Services module, this one does contain both widgets)