Respect relative_root_url when generating the mflow client integration packages_url

Summary

Reported by @devMiyax originally through #381660 (comment 1496321345):

When MLFLOW_TRACKING_URI has a directory name, mlflow.utils.autologging_utils remove it. it causes 404 error.

Steps to reproduce

1. Follow the GitLab docs to install GitLab under a relative URL.
2. Set MLFLOW_TRACKING_URI to a GitLab URL including a relative prefix.
3. Run the mlflow client.
   • Look for warning/error logs with HTTP 404 errors.

What is the current bug behavior?

The relative root is disregarded causing a HTTP 404 not found status.

What is the expected correct behavior?

The relative root is included in the mlflow packages URL.