Update SQS DSN doc sample with mention urlencode

Author: dgoujard

Diff for: docs/transport/sqs.md

@@ -29,7 +29,7 @@ $factory = new SqsConnectionFactory([
     'region' => 'aRegion',
 ]);
 
-// same as above but given as DSN string
+// same as above but given as DSN string. You may need to url encode secret if it contains special char (like +)
 $factory = new SqsConnectionFactory('sqs:?key=aKey&secret=aSecret&region=aRegion');
 
 $psrContext = $factory->createContext();