Bump FsCheck.Xunit from 2.10.4 to 2.13.0 in /exercises
Bump FsCheck.Xunit from 2.10.4 to 2.13.0 in /exercises

Bumps [FsCheck.Xunit](https://github.com/fsharp/FsCheck) from 2.10.4 to 2.13.0.
- [Release notes](https://github.com/fsharp/FsCheck/releases)
- [Changelog](https://github.com/fscheck/FsCheck/blob/master/FsCheck%20Release%20Notes.md)
- [Commits](https://github.com/fsharp/FsCheck/compare/2.10.4...2.13.0)

Signed-off-by: dependabot[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@dependabot.com>
ErikSchierboom/xfsharp,exercism/xfsharp,ErikSchierboom/fsharp