fix: update CONFIG-VARS.md for metric server (PSCLOUD-98)

[niraj2347]

PR Description
This PR updates the documentation links for the Metrics Server configuration variables.

• The current documentation references the Bitnami chart for METRICS_SERVER_CHART_URL and METRICS_SERVER_CHART_VERSION.
• However, based on our IaC code (main.yml#L29), we are not using the Bitnami chart. Instead, we are pulling from the official Kubernetes SIGs Metrics Server repo:
  • Repo: https://kubernetes-sigs.github.io/metrics-server/
  • Artifact Hub: https://artifacthub.io/packages/helm/metrics-server/metrics-server

Changes Made
Updated CONFIG-VARS.md to replace Bitnami references with the correct Kubernetes SIGs Metrics Server chart and Artifact Hub link.

Impact

• No code changes, only documentation updates.
• Ensures that the documentation correctly reflects the source of the Metrics Server Helm chart being deployed.