PLT-5860 Updated copyright date (#6058)

* PLT-5860 Updated copyright date in about modal

* PLT-5860 Updated copyright notice in JSX files

* PLT-5860 Updated copyright notice in go files

* Fixed misc copyright dates

* Fixed component snapshots

webapp/components/tutorial/tutorial_intro_screens.jsx

@@ -1,4 +1,4 @@
-// Copyright (c) 2015 Mattermost, Inc. All Rights Reserved.
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
 // See License.txt for license information.
 
 import UserStore from 'stores/user_store.jsx';

webapp/components/tutorial/tutorial_tip.jsx

@@ -1,4 +1,4 @@
-// Copyright (c) 2015 Mattermost, Inc. All Rights Reserved.
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
 // See License.txt for license information.
 
 import UserStore from 'stores/user_store.jsx';

webapp/components/tutorial/tutorial_view.jsx

@@ -1,4 +1,4 @@
-// Copyright (c) 2016 Mattermost, Inc. All Rights Reserved.
+// Copyright (c) 2016-present Mattermost, Inc. All Rights Reserved.
 // See License.txt for license information.
 
 import TutorialIntroScreens from './tutorial_intro_screens.jsx';