BUG: eps_writer.multiplot_yt regression in yt 4.1

[neutrinoceros]

Bug report

Bug summary

This bug was reported on Slack by @mihirskulkarni, I've started minimizing the reproducer script

Code for reproduction

import yt
import yt.visualization.eps_writer as eps
from yt.testing import fake_amr_ds

ds = fake_amr_ds(
    fields=[("gas", "density"), ("gas", "temperature")],
    units=["g/cm**3", "K"]
)

slc = yt.SlicePlot(
    ds,
    "y",
    [
        ("gas", "density"),
        ("gas", "temperature"),
    ],
)
eps_fig = eps.multiplot_yt(2, 1, slc)

Actual outcome

...
AttributeError: 'WindowPlotMPL' object has no attribute 'zmin'

This script worked on yt 4.0.5 and is broken since yt 4.1.0
The exact commit that this regression happened is 379c082... This is an oversight from #3849

I'll work on a patch

[neutrinoceros]

Actually it seems that the one test in yt/visualization/tests/test_eps_writer.py is broken too, so my guess is that it is currently not run on any CI.