[Fix][Connector-Mongodb] close MongodbClient when close MongodbReader (#8592)

Co-authored-by: binwang219962 <[email protected]>

Author: sohurdc

seatunnel-connectors-v2/connector-mongodb/src/main/java/org/apache/seatunnel/connectors/seatunnel/mongodb/source/reader/MongodbReader.java

@@ -82,6 +82,9 @@ public void close() {
         if (cursor != null) {
             cursor.close();
         }
+        if (clientProvider != null) {
+            clientProvider.close();
+        }
     }
 
     @Override