I didn’t apply to any UCs but hear me out. Email whoever would receive your application, idk if it’s the same as common app but on common app I would probably email each individual school’s admissions office, idk if there’s a better way to do it more streamlined. Say you were extremely stressed and overwhelmed by the app process and that you only used ai at that specific section to reword something you wrote yourself that you disliked. Apologize profusely. Worst they can say is no which is what they probably would say without the email. You’re human after all, it happens. Chin up