Close Phase and Change Task Closure

I have a reqwuirement where an RFC has to move from "Deployment" phase to "Build and Test" phase. This is a manual transition available only for change managers and Sysadmins. During this transition there is a validation message that prevents this transition. This is a maual task and not a task created using Task planner. 

"This Change may not leave the current phase until the following tasks are closed: T12345"


How can override this validation only for Change Managers  & Sysadmins? We are using 9.4 codeless.