CppTools: Remove invalid QTC_CHECK

Quitting Qt Creator before the project was loaded from the project
manager triggers the assert because the updateProjectInfo() call was not
yet made by the project manager.

Change-Id: I23c660971e48d007d1bae00ecf8ed5c2ad3d4071
Reviewed-by: Christian Stenger <christian.stenger@theqtcompany.com>
Reviewed-by: Marco Bubke <marco.bubke@theqtcompany.com>