downgrade qutip for Python 3.9 compatibility #177

Job	Run time
list-notebooks	2s
notebook (tutorials/bosonic-qiskit-textbook/2. operators.ipynb)	6m 20s
notebook (tutorials/bosonic-qiskit-textbook/3. coherent_states.ipynb)	6m 27s
notebook (tutorials/bosonic-qiskit-textbook/5. gates.ipynb)	6m 24s
notebook (tutorials/bosonic-qiskit-textbook/1. introduction.ipynb)	6m 22s
notebook (tutorials/bosonic-qiskit-textbook/4. wigner_distribution.ipynb)	6m 22s
notebook (tutorials/wigner-mle/wigner-mle.ipynb)	1s
notebook (tutorials/displacement-calibration/displacement-calibration.ipynb)	6m 23s
notebook (tutorials/wigner-function/wigner-function.ipynb)	1s
notebook (tutorials/medium_article/examples.ipynb)	1s
notebook (tutorials/jaynes-cummings-model/jaynes-cummings-dispersive.ipynb)	10s
notebook (tutorials/reduced-density-matrix/reduced-density-matrix.ipynb)	1s
notebook (tutorials/bosonic-kitten-code/bosonic-kitten-code.ipynb)	6m 25s
	44m 59s

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