Update to Vega-Lite 5.7

[binste]

VL 5.7 just got released. Updating Altair should be straight-forward as the changes to the schema itself are very small but haven't done yet as we need to wait for vega/schema#8 to be resolved. Before that, we can't run the schema generation for 5.7 as there is no 5.7 schema file yet available under https://vega.github.io/schema

[domoritz]

I fixed the schema release.