fix(integrations-guide/markdoc): add missing import in code snippets

[ArmandPhilippot]

Description (required)

We use the ImageMetadata type in 3 code snippets but we never import it; we should to make the code valid.

Related issues & labels (optional)

• Suggested label: code snippet update

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en/guides/integrations-guide/markdoc.mdx	Source changed, localizations will be marked as outdated.

Warnings reference

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🔄️	The source for this localization has been updated since the creation of this pull request, make sure all changes in the source have been applied.

[sarah11918]

LGTM, thanks!