yes, from what I have seen and tested, Security Admin or GA is needed to dismiss the risk.
Note that self -remediation is the way to go here if possible:
Hi, I want my helpdesk colleague to make use of the dismiss user risk option in the Microsoft Entra Admin Center on the Risky User Blade with minimum rights. Is Security administrator the "least" privileged role I can assign for him to do this?
Hope you got a chance to review the action plan suggested below. Please do let me know if you have any queries in the comments section. If you don't have any further queries and the suggestion works as per your business need. Please "Accept the answer(Yes)" and "share you feedback ". This will help us and others in the community as well.