Bump arviz from 0.19.0 to 0.20.0 (#328)

Bumps [arviz](https://github.com/arviz-devs/arviz) from 0.19.0 to 0.20.0.
- [Release notes](https://github.com/arviz-devs/arviz/releases)
- [Changelog](https://github.com/arviz-devs/arviz/blob/main/CHANGELOG.md)
- [Commits](arviz-devs/arviz@v0.19.0...v0.20.0)

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

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

Author: dependabot[bot]

pyproject.toml

@@ -68,7 +68,7 @@ dependencies = [
 [project.optional-dependencies]
 sk-util = ["skfolio==0.4.1", "sktime==0.33.1"]
 bayes = [
-    "arviz==0.19.0",
+    "arviz==0.20.0",
     "bambi==0.14.0",
     "pymc==5.16.2",
     "formulae==0.5.4",