cherry-pick: update docs for cloud beta (#24074)
Created by: flying-robot
Cherry-pick of https://github.com/sourcegraph/sourcegraph/pull/24074
ref Deploying to sourcegraph.com during 2021-08-19 code freeze
Created by: flying-robot
Cherry-pick of https://github.com/sourcegraph/sourcegraph/pull/24074
ref Deploying to sourcegraph.com during 2021-08-19 code freeze