DOC add link to plot_birch_vs_minibatchkmeans example in Birch (scikit-learn#29942)

Co-authored-by: adrinjalali <adrin.jalali@gmail.com>

Author: aurelienmorgan

sklearn/cluster/_birch.py

@@ -461,6 +461,9 @@ class Birch(
     subcluster are updated. This is done recursively till the properties of
     the leaf node are updated.
 
+    See :ref:`sphx_glr_auto_examples_cluster_plot_birch_vs_minibatchkmeans.py` for a
+    comparison with :class:`~sklearn.cluster.MiniBatchKMeans`.
+
     References
     ----------
     * Tian Zhang, Raghu Ramakrishnan, Maron Livny

sklearn/cluster/_kmeans.py

@@ -1838,6 +1838,9 @@ class MiniBatchKMeans(_BaseKMeans):
     always match. One solution is to set `reassignment_ratio=0`, which
     prevents reassignments of clusters that are too small.
 
+    See :ref:`sphx_glr_auto_examples_cluster_plot_birch_vs_minibatchkmeans.py` for a
+    comparison with :class:`~sklearn.cluster.BIRCH`.
+
     Examples
     --------
     >>> from sklearn.cluster import MiniBatchKMeans