Docs build timeouts with recent Cython3 change

[Xarthisius]

Bug report

Bug summary

We missed something in the most recent PR enabling Cython3...

Code for reproduction

>> Contents of the script: b95e111f    
import yt    
    
# We load the last time frame    
ds = yt.load("MOOSE_sample_data/mps_out.e", step=-1)    
    
# create a default scene    
sc = yt.create_scene(ds, ("connect2", "temp"))    
    
# override the default colormap. This time we also override    
# the default color bounds    
ms = sc.get_source()    
ms.cmap = "hot"    
ms.color_bounds = (500.0, 1700.0)    
    
# adjust the camera position and orientation    
cam = sc.camera     
camera_position = ds.arr([-1.0, 1.0, -0.5], "code_length")    
north_vector = ds.arr([0.0, -1.0, -1.0], "dimensionless")    
cam.width = ds.arr([0.04, 0.04, 0.04], "code_length")    
cam.set_position(camera_position, north_vector)    
    
# increase the default resolution    
cam.resolution = (800, 800)    
    
# render, draw the element boundaries, and save    
sc.render()    
sc.annotate_mesh_lines()    
sc.save()    
    
>> The execution of the script b95e111f took 5042.339649 s