Documenting hdbscan module to add prediction functions (#4925)

::sigh:: This was my failure. This should have been included in 22.10.

Authors:
  - Corey J. Nolet (https://github.com/cjnolet)

Approvers:
  - Dante Gama Dessavre (https://github.com/dantegd)

URL: #4925

docs/source/api.rst

@@ -420,8 +420,9 @@ Agglomerative Clustering
 HDBSCAN
 -------
 
-.. autoclass:: cuml.cluster.HDBSCAN
+.. automodule:: cuml.cluster.hdbscan
    :members:
+   :undoc-members:
 
 
 Dimensionality Reduction and Manifold Learning