refactor(go): simplify redis realtime projections

go/vehicle-gateway/internal/realtime/kv.go

@@ -109,9 +109,6 @@ func flattenKV(prefix string, value any, out map[string]any) {
 				return
 			}
 			itemKey := strconv.Itoa(index)
-			if serial := strings.TrimSpace(strconvAny(itemMap["serial_no"])); serial != "" && serial != "<nil>" {
-				itemKey = serial
-			}
 			next := itemKey
 			if prefix != "" {
 				next = prefix + "." + itemKey