Fixeswoocommerce/woocommerce-admin#6488
Changes.
* See the issue for the discussion, but we're changing the behaviour of triggering the connection flow as part of this. Before it was required that both wc-services and wc-admin were installed before triggering the flow.
* Also the plugins value was not being updated properly in the new flow, but plugins is not used in any useful way in the onboarding profile, so I have removed it completely. We now rely on the actual installed plugins to determine what is installed/activated.