feat(tf): update terragrunt dependency github.com/terraform-aws-modules/terraform-aws-eks to v20.21.0

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
github.com/terraform-aws-modules/terraform-aws-eks	github	minor	v20.20.0 -> v20.21.0

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Release Notes

terraform-aws-modules/terraform-aws-eks (github.com/terraform-aws-modules/terraform-aws-eks)

### [`v20.21.0`](https://togithub.com/terraform-aws-modules/terraform-aws-eks/releases/tag/v20.21.0) [Compare Source](https://togithub.com/terraform-aws-modules/terraform-aws-eks/compare/v20.20.0...v20.21.0) ##### Features - Add support for `upgrade_policy` ([#​3112](https://togithub.com/terraform-aws-modules/terraform-aws-eks/issues/3112)) ([e12ab7a](https://togithub.com/terraform-aws-modules/terraform-aws-eks/commit/e12ab7a5de4ac82968aaede419752ce2bbb6a93d))

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Configuration

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🚦 Automerge: Enabled.

♻ Rebasing: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox.

🔕 Ignore: Close this PR and you won't be reminded about this update again.

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