Purpose of this commit is to clean motivational capabilities of gamification
ranks[1]. It makes more sense to store a motivational to achieve on next rank
itself. We therefore rename the field and provide nice demo data that will be
used in elearning use of gamification ranks.
Commit linked to task ID 1941250 and PR #31133.
[1] task ID 1922159 (landed at 91ee6ba5a7)