chore(deps-dev): bump @vitest/coverage-istanbul from 2.1.3 to 2.1.8

Bumps [@vitest/coverage-istanbul](https://github.com/vitest-dev/vitest/tree/HEAD/packages/coverage-istanbul) from 2.1.3 to 2.1.8.
- [Release notes](https://github.com/vitest-dev/vitest/releases)
- [Commits](https://github.com/vitest-dev/vitest/commits/v2.1.8/packages/coverage-istanbul)

---
updated-dependencies:
- dependency-name: "@vitest/coverage-istanbul"
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>