Bump mlflow from 2.7.1 to 2.8.1 in /serve-jupyterlab

Bumps [mlflow](https://github.com/mlflow/mlflow) from 2.7.1 to 2.8.1.
- [Release notes](https://github.com/mlflow/mlflow/releases)
- [Changelog](https://github.com/mlflow/mlflow/blob/master/CHANGELOG.md)
- [Commits](mlflow/mlflow@v2.7.1...v2.8.1)

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

Signed-off-by: dependabot[bot] <[email protected]>

serve-jupyterlab/requirements.txt

@@ -1,3 +1,3 @@
-mlflow==2.7.1
+mlflow==2.8.1
 boto3==1.28.50 
 minio==7.1.16