add missing parameter key in code sample (#4181)

parameters should be in filter key

Resources/doc/reference/batch_actions.rst

@@ -94,7 +94,7 @@ granularity), the passed query is ``null``.
                 $this->addFlash('sonata_flash_info', 'flash_batch_merge_no_target');
 
                 return new RedirectResponse(
-                    $this->admin->generateUrl('list', $this->admin->getFilterParameters())
+                    $this->admin->generateUrl('list', array('filter' => $this->admin->getFilterParameters()))
                 );
             }
 
@@ -112,14 +112,14 @@ granularity), the passed query is ``null``.
                 $this->addFlash('sonata_flash_error', 'flash_batch_merge_error');
 
                 return new RedirectResponse(
-                    $this->admin->generateUrl('list', $this->admin->getFilterParameters())
+                    $this->admin->generateUrl('list', array('filter' => $this->admin->getFilterParameters()))
                 );
             }
 
             $this->addFlash('sonata_flash_success', 'flash_batch_merge_success');
 
             return new RedirectResponse(
-                $this->admin->generateUrl('list', $this->admin->getFilterParameters())
+                $this->admin->generateUrl('list', array('filter' => $this->admin->getFilterParameters()))
             );
         }