address unused variable lint

See: https://github.com/PrivateBin/PrivateBin/security/quality/rules/js%2Funused-local-variable

js/test/emailTemplateTest.js

@@ -1,6 +1,5 @@
 'use strict';
-var common = require('../common');
-const assert = require('assert');
+require('../common');
 
 // DOM builder that mirrors bootstrap5.php navbar
 function buildEmailDomNoShortUrl() {