It says, if I restart my computer it will install 10.10.1. I don't want it. So right now I'm trying my best to not reboot but I don't know how long I can hold off!!
My vote goes to the System Preferences suggestion.
Remain enrolled. Refrain from receiving pre-release software, for as long as you choose.
Un-enrolment may be excessive. (Without an enrolment: if you later decide to resume beta testing, then how will you be sure of (re)gaining the most up-to-date seed configuration utility? And so on.)
Postscript
I just realised, the majority of advice at https://appleseed.apple.com/sp/betaprogram/unenroll is not about un-enrolment as I know it. (To me, un-enrolment would be leaving a programme.) Apologies for any confusion.