Pin elemental-ui version repository

[e-minguez]

fleet-examples/fleets/day2/chart-templates/elemental/elemental-dashboard-extension/fleet.yaml

Line 6 in b30788d

repo: "https://github.com/rancher/ui-plugin-charts/raw/main"

https://github.com/rancher/ui-plugin-charts/blob/2.1.0/charts/elemental/2.0.0/Chart.yaml is perhaps better? (main vs 2.1.0)