fix(upgrade): Rechecks that all annotation comments have been migrated to entities

The discussion reply upgrade had a bug that caused it to mark also the comments upgrade
as completed. This rechecks whether there still are unmigrated comment annotations left
and marks the comment upgrade as incomplete if annotations are found.

Fixes #7486
Merge pull request #7489 from juho-jaakkola/fix_7486

fix(upgrade): Rechecks that all annotation comments have been migrated to entities