We had a couple places when updating review request counters where we'd fetch a `values_list` of PKs, and then pass that directly into future queries, which would end up evaluating them as subqueries. This has two problems--first, we end up running the subqueries multiple times, and second, it's impossible to use `assertQueries`. This change fixes those up. There are still cases where we have subqueries that are added by Django's `QuerySet.update()` method, but this handles the stuff in our own code. Testing Done: Verified with `assertQueries` usage that we no longer had subqueries for these.