The new MongoDB 9.0 server on sharded topology now proactively exhausts the cursor (returns cursorId: 0) when the limit is satisfied, making the emptyGetMore optimization unnecessary.
The test asserts that emptyGetMore must be called, but the server change means the code path is simply never reached - the cursor is already dead before the optimization can trigger.

The fix for NODE-6878 itself (making emptyGetMore a proper CursorResponse with all required fields for rewind()) is still valid - it just can't be exercised on this server version with sharded topology. The test needs to be relaxes to test actual regression with unwind + toArray, there is no need to validate spy on `emptyGetMore`.

Evergreen patch with 8.0 and 9.0 sharded topologies printing out server responses (note cursorId: 0):
https://spruce.corp.mongodb.com/version/69d8e357d33d560007c98599/tasks?sorts=STATUS%3AASC%3BBASE_STATUS%3ADESC

AC:

• remove spy from 'regression test (NODE-6878): CursorResponse.emptyGetMore contains all CursorResponse fields' test, validate actual unwind + toArray works on old and new mongos.