Leftover agent component docs and make targets?

[nirs]

README.md says:

1. Deploy foundation hub components on hub cluster and deploy foundation agent components on all managed clusters.

    ```sh
    make deploy-foundation
    ``` 

But make deploy-foundation deploys only the bug stuff:

$(KUSTOMIZE) build deploy/foundation/hub | $(KUBECTL) apply -f -

Looks like the agent component is part of the klusterlet operator now:

$ kubectl --context dr1 get deploy -n open-cluster-management-agent-addon 
NAME                       READY   UP-TO-DATE   AVAILABLE   AGE
klusterlet-addon-workmgr   1/1     1            1           15m

Looks like the text about agent component should be removed and/or refer
to the klusterlet operator.

The makefile includes target for the cleaning the agent compoenets:

clean-foundation-agent:
    $(KUBECTL) get managedclusteraddons -A | grep work-manager | awk '{print $$1" "$$2}' | xargs -n 2 $(KUBECTL) delete managedclusteraddons -n

But there is no code installing it in the makefile, so not sure why this code is
needed. If klusterlet-addon-workmgr is part of klusterlet, it should be removed
by klusterlet.