Fix typo in system.py

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 66.98%. Comparing base (889a34d) to head (c444a60).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## dev #508 +/- ## ======================================= Coverage 66.98% 66.98% ======================================= Files 60 60 Lines 3405 3405 ======================================= Hits 2281 2281 Misses 1124 1124 ```

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[Vaskivskyi]

Thanks, @TheCjw 👍🏻