chore(deps): bump generational-arena from 0.2.7 to 0.2.8

Bumps [generational-arena](https://github.com/fitzgen/generational-arena) from 0.2.7 to 0.2.8.
- [Release notes](https://github.com/fitzgen/generational-arena/releases)
- [Changelog](https://github.com/fitzgen/generational-arena/blob/master/CHANGELOG.md)
- [Commits](fitzgen/generational-arena@0.2.7...0.2.8)

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