Fix connection setup example in PrimaryReadReplicaConnection (#6253)

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|      Q       |   A
|------------- | -----------
| Type         | improvement
| Fixed issues | <!-- use #NUM format to reference an issue -->

#### Summary

To match other setup examples, etc.

Signed-off-by: Sora Morimoto <sora@morimoto.io>

src/Connections/PrimaryReadReplicaConnection.php

@@ -67,8 +67,8 @@
  *    'driver' => 'pdo_mysql',
  *    'primary' => array('user' => '', 'password' => '', 'host' => '', 'dbname' => ''),
  *    'replica' => array(
- *        array('user' => 'replica1', 'password', 'host' => '', 'dbname' => ''),
- *        array('user' => 'replica2', 'password', 'host' => '', 'dbname' => ''),
+ *        array('user' => 'replica1', 'password' => '', 'host' => '', 'dbname' => ''),
+ *        array('user' => 'replica2', 'password' => '', 'host' => '', 'dbname' => ''),
  *    )
  * ));
  *