Merge pull request #963 from CakeDC/5.x

minor: update documentation link to 5

Author: dereuromark

templates/layout/default.php

@@ -39,7 +39,7 @@
             <a href="<?= $this->Url->build('/') ?>"><span>Cake</span>PHP</a>
         </div>
         <div class="top-nav-links">
-            <a target="_blank" rel="noopener" href="https://book.cakephp.org/4/">Documentation</a>
+            <a target="_blank" rel="noopener" href="https://book.cakephp.org/5/">Documentation</a>
             <a target="_blank" rel="noopener" href="https://api.cakephp.org/">API</a>
         </div>
     </nav>