Bump skfolio from 0.5.2 to 0.6.0 (#367)

Bumps [skfolio](https://github.com/skfolio/skfolio) from 0.5.2 to 0.6.0.
- [Release notes](https://github.com/skfolio/skfolio/releases)
- [Changelog](https://github.com/skfolio/skfolio/blob/main/CHANGELOG.md)
- [Commits](skfolio/skfolio@v0.5.2...v0.6.0)

---
updated-dependencies:
- dependency-name: skfolio
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

pyproject.toml

@@ -66,7 +66,7 @@ dependencies = [
 ]
 
 [project.optional-dependencies]
-sk-util = ["skfolio==0.5.2", "sktime==0.34.0"]
+sk-util = ["skfolio==0.6.0", "sktime==0.34.0"]
 bayes = [
     "arviz==0.20.0",
     "bambi==0.14.0",