When featureFlagShardKeyIndexOptionalHashedSharding is enabled, index_operations_abort_concurrent_outgoing_migrations.js will drop the shard key index and verify it both aborts the chunk migration and that the index is dropped on both shards.
However, it is possible that the recipient will recreate the index before it is dropped on the donor, thus allowing it to persist even after chunk migration is aborted. This will cause the associated assertion to fail in the test.