To remove a project from Perforce control, right-click the project and choose Team>Unmanage. To verify that the project is no longer under Perforce control, right-click the project and choose Team. The only option displayed for an unmanaged project is Share Project...
Note that, although Perforce is no longer configured as the SCM provider for the project, its files remain in the depot and in your workspace. If you have any project files open in changelists, they remain open in the changelist (and can be submitted). To put the project under Perforce control again, proceed as described in Putting a Project under Perforce Control. Note that, if you have made changes to the project after removing it from Perforce control, your changes will be overwritten if you sync the files.