Fix ESLint header/header error

src/browser/components/MattermostView.jsx

@@ -1,5 +1,10 @@
+// Copyright (c) 2015-2016 Yuya Ochiai
+// Copyright (c) 2016-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
 /* eslint-disable react/no-set-state */
 // setState() is necessary for this component
+
 import url from 'url';
 
 import React from 'react';