Bump Gu.Roslyn.Extensions from 0.15.2 to 0.15.4
Bump Gu.Roslyn.Extensions from 0.15.2 to 0.15.4

Bumps [Gu.Roslyn.Extensions](https://github.com/GuOrg/Gu.Roslyn.Extensions) from 0.15.2 to 0.15.4.
- [Release notes](https://github.com/GuOrg/Gu.Roslyn.Extensions/releases)
- [Changelog](https://github.com/GuOrg/Gu.Roslyn.Extensions/blob/master/RELEASE_NOTES.md)
- [Commits](https://github.com/GuOrg/Gu.Roslyn.Extensions/commits/0.15.4)

Signed-off-by: dependabot[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@github.com>
JohanLarsson/Gu.Reactive