Update templates.rst

sonata_admin.templates.dashboard was missing

Resources/doc/reference/templates.rst

@@ -10,6 +10,7 @@ By default, an Admin class uses a set of templates, it is possible to tweak the
             # default global templates
             layout:  SonataAdminBundle::standard_layout.html.twig
             ajax:    SonataAdminBundle::ajax_layout.html.twig
+            dashboard: SonataAdminBundle:Core:dashboard.html.twig
 
             # default values of actions templates, they should extend global templates
             list:    SonataAdminBundle:CRUD:list.html.twig