Remove tests of deprecated `QubitStateVector`

[codecov[bot]]

Codecov Report

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

Project coverage is 99.42%. Comparing base (4668f36) to head (94d8640). Report is 1 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #196 +/- ## ======================================= Coverage 99.42% 99.42% ======================================= Files 8 8 Lines 350 350 ======================================= Hits 348 348 Misses 2 2 ```

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