set 2020 in license src so that syntax text do not complain

Author: archmoj

tasks/util/constants.js

@@ -124,7 +124,7 @@ module.exports = {
 
     licenseSrc: [
         '/**',
-        '* Copyright 2012-' + year + ', Plotly, Inc.',
+        '* Copyright 2012-' + '2020' + ', Plotly, Inc.',
         '* All rights reserved.',
         '*',
         '* This source code is licensed under the MIT license found in the',