Fix unit test.

Author: WaVEV

tests/model_fields_/test_arrayfield.py

@@ -454,13 +454,13 @@ def test_in_expr(self):
                 {
                     "$match": {
                         "$expr": {
-                            "$in": (
+                            "$in": [
                                 "$field",
                                 [
                                     [{"$multiply": [{"$literal": 1}, {"$literal": 1}]}],
                                     [{"$literal": 2}],
                                 ],
-                            )
+                            ]
                         }
                     }
                 }