Update CartoCell tutorial

[danifranco]

Update CartoCell tutorial describing that we have models uploaded to the zoo that can be used. Maybe an screenshot? We should discuss in how to display that info @iarganda

[iarganda]

I've created a dedicated section in the tutorial for this (commit f4f6c09):

https://biapy.readthedocs.io/en/latest/tutorials/instance_seg/cartocell.html#pre-trained-models-in-the-bioimage-model-zoo

If you think something else is necessary, please reopen the issue.

Cheers!