Merge pull request #689 from cakephp/dereuromark-patch-1

Update readme.md

Author: markstory

readme.md

@@ -39,7 +39,7 @@ public function bootstrap(): void
 
 ## Documentation
 
-Documentation for this plugin can be found in the [CakePHP Cookbook](https://book.cakephp.org/authentication/2/en/).
+Documentation for this plugin can be found in the [CakePHP Cookbook](https://book.cakephp.org/authentication/3/en/).
 
 ## IDE compatibility improvements