update leaflet and esri-leaflet

[mikofski]

latest leaflet from 2023 is 1.9.4 - see: https://leafletjs.com/

latest esri-leaflet is 3.0.16 with leaflet.js 1.9 - see: https://developers.arcgis.com/esri-leaflet/

both use unpkg, see: https://leafletjs.com/examples/quick-start/
for esri, see: https://github.com/Esri/esri-leaflet?tab=readme-ov-file#quick-start