[Bug]: Plot_connections in 3D has problem with scaling

[Ni2M]

Describe the bug 3D network's plot_connection does not work properly

https://github.com/PMEAL/OpenPNM/blob/fbb4a8d7a0204f4d85ceff3a6d112a11d7e2b02d/openpnm/topotools/plottools.py#L250 https://github.com/PMEAL/OpenPNM/blob/fbb4a8d7a0204f4d85ceff3a6d112a11d7e2b02d/openpnm/topotools/plottools.py#L289

To Reproduce

import numpy as np
import openpnm as op
import matplotlib.pyplot as plt
from openpnm import topotools
pn = op.network.Cubic(shape=[5, 8, 3])
op.topotools.plot_connections(pn)

• Autoscale doesn't work properly in 3D

[Ni2M]

refer to PR #1635