chore: fix scipy version temp lock problem and chore to master #4464

Job	Run time
pytest (ubuntu-18.04, float32, --ignore=pymc3/tests/test_backports.py --ignore=pymc3/tests/test_d...	1s
pytest (ubuntu-18.04, float32, pymc3/tests/test_dist_math.py pymc3/tests/test_distribution_defaul...	1s
pytest (ubuntu-18.04, float32, pymc3/tests/test_backports.py pymc3/tests/test_examples.py pymc3/t...	1s
pytest (ubuntu-18.04, float32, pymc3/tests/test_distributions_timeseries.py pymc3/tests/test_shap...	1s
pytest (ubuntu-18.04, float32, pymc3/tests/test_distributions.py pymc3/tests/test_gp.py pymc3/tes...	1s
pytest (ubuntu-18.04, float64, --ignore=pymc3/tests/test_backports.py --ignore=pymc3/tests/test_d...	1s
pytest (ubuntu-18.04, float64, pymc3/tests/test_dist_math.py pymc3/tests/test_distribution_defaul...	1s
pytest (ubuntu-18.04, float64, pymc3/tests/test_backports.py pymc3/tests/test_examples.py pymc3/t...	1s
pytest (ubuntu-18.04, float64, pymc3/tests/test_distributions_timeseries.py pymc3/tests/test_shap...	1s
pytest (ubuntu-18.04, float64, pymc3/tests/test_distributions.py pymc3/tests/test_gp.py pymc3/tes...	1s
	10s

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