Bump mlflow from 1.23.1 to 2.2.1 in /requirements (#151)

Bumps [mlflow](https://github.com/mlflow/mlflow) from 1.23.1 to 2.2.1.
- [Release notes](https://github.com/mlflow/mlflow/releases)
- [Changelog](https://github.com/mlflow/mlflow/blob/master/CHANGELOG.md)
- [Commits](mlflow/mlflow@v1.23.1...v2.2.1)

---
updated-dependencies:
- dependency-name: mlflow
  dependency-type: direct:production
...

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

requirements/optional.txt

@@ -3,7 +3,7 @@ ConfigSpace
 flaml==1.0.14
 hpbandster
 hyperopt==0.2.5
-mlflow==1.23.1
+mlflow==2.2.1
 nevergrad==0.4.3.post7
 optuna==2.10.0
 scikit-learn