[docs-scanner] Potentially stale multi-platform prerequisites section

[docker-agent]

File: content/manuals/build/building/multi-platform.md

Issue

The Prerequisites section presents containerd image store as an optional alternative to creating a custom builder. This framing may be outdated if containerd is now the default or recommended approach:

To build multi-platform images, you first need to make sure that your Docker
environment is set up to support it. There are two ways you can do that:

• You can switch from the "classic" image store to the containerd image store.
• You can create and use a custom builder.

The section describes "switching" to containerd, which implies it's not the default. If containerd is now standard in recent Docker Desktop/Engine versions, this creates confusion about what users actually need to do.

Suggested fix

Verify the current state:

1. If containerd is now default in supported Docker versions, update to reflect that users likely already have it
2. If it's still optional, clarify which Docker versions require manual setup
3. Consider adding version-specific guidance rather than presenting both options as equally valid

The goal is to help users understand whether they need to take action based on their Docker version.

---

Found by nightly documentation freshness scanner

[dvdksn]

Fixed in #24327