Maintenance: add China layers to docs + clean old workflows

[dreamorosi]

Summary

In #3920 we added workflows to start publishing Lambda layers to AWS China regions. Once the work is complete and deployment in Gamma is verified we can remove the older workflows that were GovCloud specific and update the docs + the script that updates the ARN during releases.

Why is this needed?

So that we can complete the action item.

Which area does this relate to?

Other

Solution

No response

Acknowledgment

• This request meets Powertools for AWS Lambda (TypeScript) Tenets
• Should this be considered in other Powertools for AWS Lambda languages? i.e. Python, Java, and .NET

Future readers

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[powertools-for-aws-oss-automation]

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