docs(model-roles/embeddings): fix dead www.voyageai.com link

[sanjibani]

Replaces https://www.voyageai.com/ (404 via www subdomain) with https://voyageai.com/dashboard (200).

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Summary by cubic

Fixes a dead Voyage AI link in the embeddings docs by replacing https://www.voyageai.com/ with https://voyageai.com/dashboard. This points users directly to the API key page.

^{Written for commit 4863138. Summary will update on new commits.}

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[cubic-dev-ai]

No issues found across 1 file

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