Remove docker metrics export via telegraf agent

What does this MR do and why?

Now that we have our own E2E runner infrastructure, it's more efficient to measure resource utilisation through runner itself rather than one specific deployment type.

This removes custom metrics export via telegraf container.

Closes: gitlab-org/quality/quality-engineering/team-tasks#2756 (closed)

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• Commits include Changelog: trailer
• I have evaluated the MR acceptance checklist for this MR.