🐛 Bug: Now-unnecessary no-unsafe-assignment disable in ESLint config for test files

### Bug Report Checklist

- [x] I have tried restarting my IDE and the issue persists.
- [x] I have pulled the latest `main` branch of the repository.
- [x] I have [searched for related issues](https://github.com/JoshuaKGoldberg/create-typescript-app/issues?q=is%3Aissue) and found none that matched my issue.

### Expected

Now that https://github.com/vitest-dev/vitest/pull/7016 is merged, created ESLint configs shouldn't need to disable any `no-unsafe-*` rules in test files.

### Actual

https://github.com/JoshuaKGoldberg/create-typescript-app/blob/94e253e7c5922dd2818e9cf7e3540ae43ba794e8/eslint.config.js#L91C32-L91C53

### Additional Info

Looks like the upstream PR was reverted for the current major version in https://github.com/vitest-dev/vitest/pull/8129:

> The team decided to revert the change until the next major version.

Marking this as blocked until Vitest ~~8~~ 4.

🎁

Start at the test-file configuration in eslint.config.js around line 91 and review the linked Vitest changes to confirm when the no-unsafe-* suppression is no longer needed. Once the supported Vitest major version is available, remove the unnecessary disable and run the repository's lint and test checks to verify the generated configuration.

Written by the indexing model from the issue text.