[docs-scanner] Invalid registry image version in trust sandbox compose file

[github-actions]

File: content/manuals/engine/security/trust/trust_sandbox.md

Issue

The compose.yaml example specifies an invalid registry image version:

sandboxregistry:
  image: registry:3

The official Docker registry image does not have a version 3. The current stable version is 2.x (specifically, the latest is registry:2.8.x). Using registry:3 would cause the sandbox setup to fail when users try to run docker compose up -d.

Why this matters

Readers following this tutorial will encounter an immediate failure when trying to build the sandbox:

Error response from daemon: manifest for registry:3 not found

This breaks the tutorial at the very first step, preventing users from experimenting with Docker Content Trust as intended. The error provides no clear guidance about what went wrong.

Suggested fix

Change the registry image to use a valid version:

sandboxregistry:
  image: registry:2

Or use a specific stable version like registry:2.8 if version pinning is preferred for tutorial stability.

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Found by nightly documentation quality scanner

[dvdksn]

I know man, I also find it hard to believe sometimes, that there is actually a 3.x out. It was long anticipated, but it finally happened! Kudos to the distribution maintainers, really. Much love to those folks.