update vega and vega-lite

[mikofski]

the latest version is v6.1, see: https://vega.github.io/vega-lite/tutorials/getting_started.html

    <script src="https://cdn.jsdelivr.net/npm/vega@6.0.0"></script>
    <script src="https://cdn.jsdelivr.net/npm/vega-lite@6.1.0"></script>
    <script src="https://cdn.jsdelivr.net/npm/vega-embed@6.29.0"></script>