Pin Docker digests

This MR contains the following updates:

Package	Type	Update	Change
alpine		pin	3.10.1 -> 3.10.1@6a92cd1
docker	image	pin	19.03.1 -> 19.03.1@021de03
docker	service-image	pin	19.03.1-dind -> 19.03.1-dind@51db44d
koalaman/shellcheck-alpine	image	pin	v0.7.0 -> v0.7.0@169a51b

📌 Important: Renovate will wait until you have merged this Pin MR before creating any upgrade MRs for the affected packages. Add the preset :preserveSemverRanges your config if you instead don't wish to pin dependencies.

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Renovate configuration

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🚦 Automerge: Enabled.

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👻 Immortal: This MR will be recreated if closed unmerged. Get config help if that's undesired.

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• If you want to rebase/retry this MR, check this box