Notebooks tests failing on MacOs due to exceeded time limit

[EnricoTrizio]

Some notebook tests fail on MacOs because some cell takes more than 300s to finish.
It happens randomly (sometimes it does sometimes it doesn't) but still it's annoying.

Should we check this in the tutorials and maybe use fake values and comment the real ones?

[andrrizzi]

That sounds like a good idea to me. Maybe explaining that the commented value is a better default and the de-commented value makes the execution quick but won't necessarily give good results.