Remove future annotations to fix issue with ClassVar ForwardRef

[codecov[bot]]

Codecov Report

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

Project coverage is 91.36%. Comparing base (6fb6b50) to head (efc9a02).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #137 +/- ## ========================================== - Coverage 91.36% 91.36% -0.01% ========================================== Files 23 23 Lines 1471 1470 -1 ========================================== - Hits 1344 1343 -1 Misses 127 127 ```

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[GDYendell]

Fixed in https://github.com/pydantic/pydantic/pull/10347