I don't think this is going to work.
a) You gave them a license to use your answers. It is not revokable.
b) You *can* and *should* ask to be disassociated from your answers. AFAIK, this satisfies any GDPR requirements. (If you don't think so, please explain.)
Source: I used to be deeply involved in the moderation on that site before the enshittification made me quit some years back.
@yourautisticlife @ben
That said the licence is a CC license, correct? Use of that data to train an AI model would remove the attribution that's required; though I'm sadly aware that big tech doesn't seem to care about that and the courts haven't yet stopped them. :P