numpy not in pyproject.toml file

[clausmichele]

Recently numpy version 2 came out: https://numpy.org/devdocs/release/2.0.0-notes.html
It might break some functionality, in my opinion we should fix the numpy version to <2 in the pyproject.toml file, until some testing has been carried out. What do you think @ValentinaHutter ?

[ValentinaHutter]

Thanks for pointing this out, I agree!

#312