As part of SERVER-36381 we added a test to stress running an $out during the 4.0 -> 4.2 upgrade. This test can be removed once we branch for 4.2 since it was targeted at making sure the cluster can correctly handle the "legacy" {$out: "name"}-style syntax even though it is internally upgraded to the newer: {$out: {to: "name", ...}} syntax internally. Once we're only concerned with the 4.2 -> 4.4 upgrade, all versions will understand both syntaxes, so this test can be removed.