Apply suggestions from code review

Co-Authored-By: Oskar Stark <oskarstark@googlemail.com>

Author: Joe Bennett

components/lock.rst

@@ -289,17 +289,18 @@ The MongoDbStore saves locks on a MongoDB server, it requires a
 ``\MongoDB\Client`` connection from `mongodb/mongodb`_. This store does not
 support blocking and expects a TTL to avoid stalled locks::
 
+    use MongoDB\Client;
     use Symfony\Component\Lock\Store\MongoDbStore;
 
-    $mongoClient = new \MongoDB\Client('mongo://localhost/');
+    $client = new Client('mongo://localhost/');
 
     $options = [
         'database' => 'my-app',
     ];
 
-    $store = new MongoDbStore($mongoClient, $options);
+    $store = new MongoDbStore($client, $options);
 
-The ``MongoDbStore`` takes the following ``$options``:
+The ``MongoDbStore`` takes the following options:
 
 ============  =========  ========================================================================
 Option        Default    Description