updated docstrings for Qobj.eliminate_states and Qobj.extract_states
updated docstrings for Qobj.eliminate_states and Qobj.extract_states

anubhavvardhan/qutip,zasdfgbnm/qutip,cgranade/qutip,zasdfgbnm/qutip,cgranade/qutip,qutip/qutip,anubhavvardhan/qutip,qutip/qutip