Removed duplicate statement in example code

`client = client = ` does not make that much sense 🤔

Author: lennartk

source/drivers/motor.txt

@@ -56,7 +56,7 @@ To connect to a `MongoDB Atlas <https://docs.atlas.mongodb.com/>`_ cluster, use
 
    import motor
 
-   client = client = motor.motor_tornado.MotorClient(
+   client = motor.motor_tornado.MotorClient(
       "mongodb+srv://<username>:<password>@<cluster-url>/test?retryWrites=true&w=majority")
    db = client.test