fix matplotlib deprecated

[FabriceSalvaire]

/opt/python-virtual-env/py38/lib/python3.8/site-packages/Pyterate-2.1.5-py3.8.egg/Pyterate/RstFactory/Evaluator/FigureTools.py:54: MatplotlibDeprecationWarning: savefig() got unexpected keyword argument "papertype" which is no longer supported as of 3.3 and will become an error two minor releases later
  figure.savefig(

/home/fabrice/pyspice/PySpice/Plot/BodeDiagram.py:46: MatplotlibDeprecationWarning: The 'basex' parameter of __init__() has been renamed 'base' since Matplotlib 3.3; support for the old name will be dropped two minor releases later.
  axe.semilogx(frequency, phase, basex=10, **kwargs)

[FabriceSalvaire]

https://matplotlib.org/stable/api/figure_api.html?highlight=savefig#matplotlib.figure.Figure.savefig
papertype ???