remove dangerous stop as backup mode

app/UI/Backup/Forms/CreateForm.php

@@ -77,8 +77,7 @@ class CreateForm extends BaseForm implements ClientArea
         $field = new Select('mode');
         $field->setAvailableValues([
             "snapshot" => sl("lang")->tr("Snapshot"),
-            "suspend"  => sl("lang")->tr("Suspend"),
-            "stop"     => sl("lang")->tr("Stop")
+            "suspend"  => sl("lang")->tr("Suspend")
         ]);
         $this->addField($field);
     }