chore: remove js-green-licenses (#7201)

scripts/gulpfiles/license_tasks.js

@@ -1,22 +0,0 @@
-/**
- * @license
- * Copyright 2018 Google LLC
- * SPDX-License-Identifier: Apache-2.0
- */
-
-/**
- * @fileoverview Gulp tasks to check the licenses of Blockly dependencies.
- */
-
-const jsgl = require('js-green-licenses');
-
-function checkLicenses() {
-  const checker = new jsgl.LicenseChecker();
-  checker.setDefaultHandlers();
-  return checker.checkLocalDirectory('.');
-};
-
-module.exports = {
-  // Manually-invokable targets, with prerequisites where required.
-  checkLicenses: checkLicenses
-};