[DOC] - Write documentation for amazon_web_services.eks_kms_arn config option

[joneszc]

Preliminary Checks

• This issue is not a question, feature request, RFC, or anything other than a bug report. Please post those things in GitHub Discussions: https://github.com/nebari-dev/nebari/discussions

Summary

Pending the merge of PR#2788, new functionality is enabled, optionally, for a user to specify an ARN of a symmetric AWS KMS key, which must be set for encrypt and decrypt, to employ in implementing EKS cluster secrets encryption.

Steps to Resolve this Issue

1. Add a section to the amazon_web_services Provider docs detailing advanced config setting for EKS KMS ARN (Optional)

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