Update docker/dockerfile Docker tag to v1.9 - autoclosed

[balena-renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
docker/dockerfile	syntax	minor	1.2 -> 1.9

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Configuration

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🚦 Automerge: Enabled.

♻ Rebasing: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox.

🔕 Ignore: Close this PR and you won't be reminded about this update again.

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This PR has been generated by Renovate Bot.