chore: retire layer generator

[ava-silver]

What does this PR do?

• Removes the AWS-latest layer generator.
• Removes release-time AWS layer updates.

Motivation

The central Lambda catalog becomes the only layer-update source after cutover.

Testing Guidelines

No manual validation.

Additional Notes

Do not merge until #725 and #726 merge, and the serverless-ci renderer has reproduced runtime-catalog.json, layers.json, and layers-gov.json, including architecture, FIPS, fallback, and regional-exception behavior.

Types of changes

• Bug fix
• New feature
• Breaking change
• Misc (docs, refactoring, dependency upgrade, etc.)

Check all that apply

• This PR's description is comprehensive
• This PR contains breaking changes that are documented in the description
• This PR introduces new APIs or parameters that are documented and unlikely to change in the foreseeable future
• This PR impacts documentation, and it has been updated (or a ticket has been logged)
• This PR's changes are covered by the automated tests
• This PR collects user input/sensitive content into Datadog

[ava-silver]

• chore: retire layer generator #727 👈 (View in Graphite)
• main

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