fix: change qmc test device to pennylane default instead of lightning

[ashlhans]

Issue #, if available:

Description of changes:

Testing done:

Merge Checklist

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[codecov[bot]]

Codecov Report

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

Comparison is base (67ac8e5) 100.00% compared to head (8d6f1fa) 100.00%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #136 +/- ## ========================================= Coverage 100.00% 100.00% ========================================= Files 26 26 Lines 1028 1028 Branches 181 181 ========================================= Hits 1028 1028 ```

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