Pin numpy version to avoid segmentation fault

[montanarograziano]

Describe the bug
Related to #159.
As described in this polars issue, Numpy 2.0 is not supported and causes troubles. This should be fixed in the next Polars release, but until then Numpy version should be pinned, as it may cause troubles in development.

To Reproduce
Bug is probably not related only to plot_panel method.

data = pl.read_parquet("data/commodities.parquet")
plot_panel(y=y)

Desktop (please complete the following information):

• OS: MacOs
• Version Ventura