Add PVEAuditor role to Proxmox docs

[matuzalemmuller]

What does this PR do?

Add PVEAuditor role to Proxmox docs. The current version of the documentation does not specify the permissions needed by the token.

PVEAuditor provides read-access to the API endpoints, thus giving enough permissions for the datadog agent to query PVE.

Motivation

Lack of information in the current version of the documentation.

Review checklist (to be filled by reviewers)

• Feature or bugfix MUST have appropriate tests (unit, integration, e2e)
• Add the qa/skip-qa label if the PR doesn't need to be tested during QA.
• If you need to backport this PR to another branch, you can add the backport/<branch-name> label to the PR and it will automatically open a backport PR once this one is merged

[github-actions]

⚠️ Recommendation: Add qa/skip-qa label

This PR does not modify any files shipped with the agent.

To help streamline the release process, please consider adding the qa/skip-qa label if these changes do not require QA testing.

[sarah-witt]

Thank you!