Update PyPlot.py

[renaudponcelet]

w_xaxis, w_yaxis and w_zaxis are deprecated (https://matplotlib.org/stable/api/prev_api_changes/api_changes_3.6.0.html).

[andrewjessop]

I too had this problem, running:

$ pip list | egrep "matplotlib|spatialmath-python|roboticstoolbox-python"
matplotlib                        3.8.2
matplotlib-inline                 0.1.3
roboticstoolbox-python            1.1.0
spatialmath-python                1.1.9

[petercorke]

Thanks for your interest in the toolbox. This PR has been merged into future branch, not yet on PyPI.