docs(AMI): make AMI public in us-east-2 and clarify region/visibility so users can find it

[neubig]

Summary

• Make the WebArena AMI public in us-east-2 (Ohio) and ensure the backing snapshot is also public so any account can launch it in that region.
• Update environment_docker/README.md to clearly document region scoping and visibility.

Changes

• AWS:
  • Set AMI ami-08a862bf98e3bd7aa launch permissions to public (Group=all) in us-east-2.
  • Set snapshot snap-07d315b778cc402cc createVolumePermission to public (Group=all).
  • Re-enabled account-level "block-new-sharing" after making the AMI public to prevent accidental future sharing.
• Docs:
  • environment_docker/README.md now includes:
    • Region: us-east-2 (Ohio)
    • Visibility: Public (available to all accounts in us-east-2)
    • A note reminding users to switch their EC2 console region to us-east-2 if they cannot find the AMI.

Why
Users reported they could not find the AMI. The image existed only in us-east-2 and was private to the owner account. Making it public and documenting the region resolves the issue.

Testing/Verification

• Verified via AWS API:
  • AMI Public: True, LaunchPermissions: [{Group: all}]
  • Snapshot permissions: [{Group: all}]
• Confirmed the AMI is discoverable in us-east-2. Other regions will not show this AMI ID (region-scoped).

Notes

• The AMI is only published in us-east-2. If regional availability is desired elsewhere, we can copy the AMI to additional regions and apply the same visibility settings.

Checklist

• Update docs to clarify region and visibility
• Ensure AMI and backing snapshot are publicly launchable in us-east-2
• Keep account-level block-new-sharing enabled post-change

Fixes #225

@neubig can click here to continue refining the PR

[openhands-ai]

Looks like there are a few issues preventing this PR from being merged!

• GitHub Actions are failing:
  • Python Package Pytest

If you'd like me to help, just leave a comment, like

@OpenHands please fix the failing actions on PR #227 at branch `docs/make-ami-public-clarify-region-us-east-2`

Feel free to include any additional details that might help me get this PR into a better state.

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