Bug 1416153 - Part 2: Remove now unused variable. r=bustage

browser/base/content/test/siteIdentity/browser_insecureLoginForms.js

@@ -131,7 +131,6 @@ add_task(async function test_mixedcontent() {
  * Checks that insecure window.opener does not trigger a warning.
  */
 add_task(async function test_ignoring_window_opener() {
-  let newTabURL = "https://example.com" + TEST_URL_PATH + "form_basic.html";
   let path = getRootDirectory(gTestPath)
     .replace("chrome://mochitests/content", "http://example.com");
   let url = path + "insecure_opener.html";