[Tests] fix tests in node 3

Author: ljharb

package.json

@@ -44,6 +44,7 @@
 		"browserify": "^17.0.1",
 		"eslint": "=8.8.0",
 		"nyc": "^10.3.2",
+		"object.assign": "^4.1.7",
 		"tape": "^5.9.0"
 	},
 	"dependencies": {

test/index.js

@@ -205,10 +205,12 @@ function runTests(name, compat) {
 var js = require('../browser');
 runTests('JavaScript pbkdf2', js);
 
+var assign = require('object.assign');
+
 /* istanbul ignore next */
 if (!process.browser) {
 	/* eslint global-require: 0 */
-	var browser = Object.assign({}, js);
+	var browser = assign({}, js);
 	browser.pbkdf2Sync = require('../lib/sync-browser');
 	runTests('browser pbkdf2', {
 		pbkdf2: browser.pbkdf2,