chore(docker): update owncloud/ubuntu:20.04-arm64v8 docker digest to 8dc986d

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
owncloud/ubuntu	final	digest	b86b8d2 -> 8dc986d
owncloud/ubuntu	final	digest	3cbedb3 -> c9fd042
owncloud/ubuntu	final	digest	440fe53 -> 98b01ae

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