Remove unused dagre-d3 dependency

[rak-phillip]

Summary

This removes the unused dagre-d3 dependency from Dashboard and Shell.

dagre-d3 was originally introduced via #139; this feature has since been removed, yet the dagre-d3 dependency remained.

This PR should close a high security alert for d3-color: https://github.com/rancher/dashboard/security/dependabot/102

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[rak-phillip]

@aalves08 I would like you to review because you were the original author of the Fleet ForceDirectedTreeChart. While that appears to use both d3 and d3-selection, I don't see any indication that dagre-d3 is required in any way.