Repair tests

[Conengmo]

Seems like a new pandas version got out that deprecated some things in three notebook. Let's see if everything runs okay now.

• Altair 5.0.0 has a fix to work with the new Pandas version, so pin that.
• New Altair version doesn't have data built in, use the vega_datasets package instead.
• Some notebooks needed some syntax fixes to work with the new Pandas version.
• Don't test the code of examples/WmsTimeDimension.ipynb, the external resource makes it flaky. We already skip it in the Selenium tests.

[Conengmo]

There’s an issue with installing the packages on Python 3.7. Since that version will be end of line soon, I’ll upgrade the workflow to 3.8.

[Conengmo]

Everything passes! 🚀