[Docs]: Remind release engineers to update shared docs after each release #843

Requested change

Update RELEASE.md to remind release engineers to review and update aws/aws-durable-execution-docs after each new Java release. This is a documentation-only change to the human release process.

The existing "Update the shared documentation" section in RELEASE.md reminds engineers to update literal dependency versions. Expand that section to cover released APIs, behavior, and examples as well.

Why

Docs PR #300 was needed to catch references and examples up with released Java, TypeScript, and Python functionality, including SDK 3 plugin factories, serialization, telemetry, and testing APIs. A reminder in the release instructions should help prevent this drift.

Release checklist guidance

• Expand section 4, "Update the shared documentation," with an explicit checklist for the release engineer after publication is verified.
• Link directly to the shared docs repository and remind the engineer to review the changes in every package released, including testing and plugin packages when applicable.
• Update affected API references, guides, and examples/java/ snippets, along with dependency versions, compatibility guidance, and migration instructions as needed. Checking version strings alone is insufficient.
• Ask the engineer to open or update the relevant docs PR, link the SDK release, run the docs repository's applicable checks, and follow through on review and merge. If the release needs no docs changes, record that the review was completed.

Acceptance criteria

• The release instructions clearly assign the docs review/update to the release engineer for every new version release.
• The reminder identifies the docs repository and covers changed behavior and examples as well as version numbers.
• Changes are limited to the release guide/checklist.