DOCSP-51630 Add admonition for minPoolSize behavior (#1190)

Author: stephmarie17

source/connect/connection-options/connection-pools.txt

@@ -165,6 +165,18 @@ object:
      minPoolSize: 10
    });
 
+.. note::
+
+   A ``MongoClient`` configured with ``maxIdleTimeMS`` and ``minPoolSize`` 
+   set to ``0`` is optimal for workloads with sustained periods of low activity. 
+   This configuration allows the connection pool to close unused connections 
+   during periods of inactivity. 
+   
+   In versions earlier than 6.18.0, the {+driver-short+} did not close idle
+   connections when ``minPoolSize`` was set to ``0`` during periods of
+   inactivity. Starting in version 6.18.0, the connection pool correctly closes
+   idle connections regardless of the ``minPoolSize`` setting.
+
 .. _node-connection-pool-max-idle-time:
 
 maxIdleTimeMS