IONOS(config): switch submodule (viewer) to ionos nc-viewer

[printminion-co]

Summary

• Switch to custom nc-viewer (as for now same sha - our repo)
• Update to https://github.com/nextcloud/viewer/releases/tag/v29.0.5

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)

[tanyaka]

Review OK.

[github-actions]

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