Bug in the rendering of the process matrix

[BoxiLi]

Bug Description

The rendering of the process matrix looks weird in qutip-v5, The bottom of the bars behind is on top of the lower bars in front of it. (This is a CNOT gate with some errors)

Maybe the order of the bar rendering is reversed during the last refactoring of the plotting library?

Code to Reproduce the Bug

No response

Code Output

No response

Expected Behaviour

The bars should be rendered correctly.

Your Environment

QuTiP Version:      5.0.1
Numpy Version:      1.26.4
Scipy Version:      1.12.0
Cython Version:     None
Matplotlib Version: 3.8.3
Python Version:     3.11.8
Number of CPUs:     40
BLAS Info:          Generic
INTEL MKL Ext:      False
Platform Info:      Linux (x86_64)

Additional Context

No response