Publish v1.21.0 [release]

[JalexChen]

For our official CircleCI Docker Convenience Image support policy, please see CircleCI docs.

This policy outlines the release, update, and deprecation policy for CircleCI Docker Convenience Images.

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Description

Re-release Go 1.21 due to issues raised in this PR pertaining to breaking changes related to upstream packages for go-critic, kubernetes, and gocilint

Reasons

Please provide reasoning for these changes and how this PR achieves them.

• Provided feedback on the PR and gave time for a rebase on the branch. Incorporated their PR so they get contribution credit
• Per my comments on the PR, the breaking changes should necessitate a re-release to prevent breaking builds due to the linter

If applicable, include a link to the related GitHub issue that this PR will close.

Checklist

Please check through the following before opening your PR. Thank you!

• I have made changes to the Dockerfile.template file only
• I have not made any manual changes to automatically generated files
• My PR follows best practices as described in the contributing guidelines
• (Optional, but recommended) My commits are signed

[ryanbourdais]

LGTM