fix: remove group to preserve compatibility

[vkWeb]

Summary

Removes group to fix errors generated due to outdated objects on db.

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Reviewer checklist

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[vkWeb]

cc @rtibbles @radinamatic for review.

[rtibbles]

Solves this specific issue - seems like we might need to stop pickling to handle the class of errors more generally.

[vkWeb]

Yes, I agree.

After we finish decoupling the tasks and simplifying workers, we'll look into how to stop pickling altogether.