Switch to uber/npm-shrinkwrap for npm-shrinkwrap.json generation

Instead of our homegrown grunt/shrinkwrap.js
Fixes #13483.
New npm-shrinkwrap.json is human-readable but still in a consistent/stable format.
Should aid debugging, produce better diffs, and be less prone to merge conflicts

grunt/shrinkwrap.js

@@ -1,41 +0,0 @@
-/*!
- * Bootstrap Grunt task for generating npm-shrinkwrap.canonical.json
- * http://getbootstrap.com
- * Copyright 2014 Twitter, Inc.
- * Licensed under MIT (https://github.com/twbs/bootstrap/blob/master/LICENSE)
- */
-/*
-This Grunt task updates the npm-shrinkwrap.canonical.json file that's used as the key for Bootstrap's npm packages cache.
-This task should be run and the updated file should be committed whenever Bootstrap's dependencies change.
-*/
-'use strict';
-var canonicallyJsonStringify = require('canonical-json');
-var NON_CANONICAL_FILE = 'npm-shrinkwrap.json';
-var DEST_FILE = 'test-infra/npm-shrinkwrap.canonical.json';
-
-
-function cleanup(shrinkwrap) {
-  // Remove `resolved` property to avoid irrelevant changes
-  // See https://github.com/npm/npm/issues/3581
-  if (typeof shrinkwrap === 'string') {
-    return shrinkwrap;
-  }
-  delete shrinkwrap.resolved;
-  for (var key in shrinkwrap) {
-    shrinkwrap[key] = cleanup(shrinkwrap[key]);
-  }
-  return shrinkwrap;
-}
-
-function updateShrinkwrap(grunt) {
-  // Assumption: Non-canonical shrinkwrap already generated by prerequisite Grunt task
-  var shrinkwrapData = grunt.file.readJSON(NON_CANONICAL_FILE);
-  grunt.log.writeln('Deleting ' + NON_CANONICAL_FILE.cyan + '...');
-  grunt.file.delete(NON_CANONICAL_FILE);
-  // Output as Canonical JSON in correct location
-  grunt.file.write(DEST_FILE, canonicallyJsonStringify(cleanup(shrinkwrapData)));
-  grunt.log.writeln('File ' + DEST_FILE.cyan + ' updated.');
-}
-
-
-module.exports = updateShrinkwrap;