The original code caused Rails to generate invalid SQL. The problem
lays in the `.arel` method in `ActiveRecord::Relation`. When there was
a `limit` on the relation, the `LIMIT` statement was taken over to
Arel, but the value wasn't.

```ruby
relation = Event.limit(2)
relation.to_sql
#=> "SELECT  `events`.* FROM `events` LIMIT 2"
relation.arel.to_sql
#=> "SELECT  `events`.* FROM `events` LIMIT ?"
```

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/51729