Update metrics-server helm chart to 3.8.1

[naris-silpakit]

What does this PR do?

Updates the helm chart for metrics-server to 3.8.1. Also updated examples and documentation that reference a helm chart version for metrics-server to 3.8.1.

More

• Yes, I have tested the PR using my local account setup (Provide any test evidence report under Additional Notes)
• Yes, I have added a new example under examples to support my PR
• Yes, I have created another PR for add-ons under add-ons repo (if applicable)
  • update metrics-server to helm chart 3.8.1 aws-samples/eks-blueprints-add-ons#15
• Yes, I have updated the docs for this feature
• Yes, I ran pre-commit run -a with this PR

Note: Not all the PRs required examples and docs except a new pattern or add-on added.

For Moderators

• E2E Test successfully complete before merge?

Additional Notes

Testing notes:

• created test directory and filled main.tf file with vpc, eks cluster with metrics server addon enabled
• ran terraform apply -auto-approve and checked that deployment completes
• ran kubectl logs -n kube-system <pod> to check logs for errors

[vara-bonthu]

LGTM!