matplotlib ax.change_geometry deprecation

[kecnry]

will be removed in matplotlib 3.6

axes.py:1011: MatplotlibDeprecationWarning: 
The change_geometry function was deprecated in Matplotlib 3.4 and will be removed two minor releases later. Use set_subplotspec instead.
  ax.change_geometry(rows, cols, i+1)

[kecnry]

basics are implemented in 93e6deb, but would still like to have more consistent subplot spacing between the two implementations. It seems that tight_layout no longer behaves as nicely from within autofig and often need to call plt.tight_layout manually to avoid automatic padding between axes (depending on figure size). See the subplot positioning tutorial, for a good test case.