Increase ulimit in notebook test actions

[frankharkins]

Hopefully fixes #2387. See https://ss64.com/bash/ulimit.html for more information.

[arnaucasau]

Let's see if this solves the problem. As a caveat, I read in the man bash pages that the option -n is not allowed to be set on most systems, have you tried running this in CI?

[frankharkins]

Thanks! Yep, the command ran without error (see https://github.com/Qiskit/documentation/actions/runs/12282805213/job/34274824747#step:5:575), although it's possible it could fail silently.