updateProposal should implement the same arguments are updateProposals

As you see here, the "proposal" function does not take the "apolloQueryOptions" argument.
https://github.com/daostack/arc.js/blob/client-2-0/src/arc.ts#L278, as the `proposals()` function does a few lines higher up.

This is actually useful if you are checking for existence of the proposal and want to bypass the cache,