[llvm] [docs] Remove myself from security response (PR #203061)

[Kristof Beyls via llvm-commits]

kbeyls wrote:

> > Do we need to manually sync this to other places? e.g. group membership and rotation members
> 
> Yes there are a few things to do, I'll look into doing that and will respond here when done.

I've removed @cuviper now from the private security response team mailing list and from the github team that gives access to undisclosed security issues. @gburgessiv : I think the only thing left to do is to remove @cuviper from the rota schedule. Would you be OK with doing that?

I think this PR can now be merged without the danger of us forgetting about removing access to systems for @cuviper .

https://github.com/llvm/llvm-project/pull/203061