Update counter-cache.rst (#7927)

Update counter-cache.rst

Refs cakephp/cakephp#17966

en/orm/behaviors/counter-cache.rst

@@ -131,6 +131,14 @@ then updates the counter of the *previously* associated item.
     behavior to the ``CommentsTable`` in order to generate ``comment_count`` for
     Articles table.
 
+.. versionchanged:: 5.1.2
+
+    As of CakePHP 5.1.2, the counter cache values are updated using a single
+    query using sub-queries, instead of separate queries, to fetch the count and
+    update a record. If required you can disable the use of sub-queries by
+    setting `useSubQuery` key to `false` in the config
+    `['Articles' => ['comment_count' => ['useSubQuery' => false]]`
+
 Belongs to many Usage
 =====================