agg_mongos_merge.js currently reads the featureFlag value of featureFlagShardedLookup without checking whether the field exists. However, it's possible that this will fail against multiversion tests when we start running it in suites that execute against 5.0/5.1 binaries since it looks like the feature flag doesn't exist on 5.0.

For now, the tests are blacklisted from multiversion testing because of the requires_fcv_47 flag. However, this tag will no longer be in use after https://jira.mongodb.org/browse/SERVER-56366.