Bump vitest in /packages/itwin/grouping-mapping-widget

Bumps [vitest](https://github.com/vitest-dev/vitest/tree/HEAD/packages/vitest) from 3.0.0 to 3.2.6.
- [Release notes](https://github.com/vitest-dev/vitest/releases)
- [Changelog](https://github.com/vitest-dev/vitest/blob/main/docs/releases.md)
- [Commits](https://github.com/vitest-dev/vitest/commits/v3.2.6/packages/vitest)

---
updated-dependencies:
- dependency-name: vitest
  dependency-version: 3.2.6
  dependency-type: direct:development
...

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