## What changes were proposed in this pull request?
Since we done Scala API audit for ml.clustering at #13148, we should also fix and update the corresponding Python API docs to keep them in sync.

## How was this patch tested?
Docs change, no tests.

Author: Yanbo Liang <ybliang8@gmail.com>

Closes #13291 from yanboliang/spark-15361-followup.