[skip ci][doc] Update link

Author: makasim

pkg/dsn/README.md

@@ -3,7 +3,7 @@
 ## Resources
 
 * [Site](https://enqueue.forma-pro.com/)
-* [Documentation](https://github.com/php-enqueue/enqueue-dev/blob/master/docs/index.md)
+* [Documentation](https://github.com/php-enqueue/enqueue-dev/blob/master/docs/dsn.md)
 * [Questions](https://gitter.im/php-enqueue/Lobby)
 * [Issue Tracker](https://github.com/php-enqueue/enqueue-dev/issues)