Bug 1711681: Update PBM tests within dom/tests to work with https-first-mode enabled r=emilio

Differential Revision: https://phabricator.services.mozilla.com/D115367

dom/tests/browser/browser_bug1563629.js

@@ -6,8 +6,8 @@ const DIRPATH = getRootDirectory(gTestPath).replace(
 );
 const PATH = DIRPATH + "file_postMessage_parent.html";
 
-const URL1 = `http://example.com/${PATH}`;
-const URL2 = `http://example.org/${PATH}`;
+const URL1 = `https://example.com/${PATH}`;
+const URL2 = `https://example.org/${PATH}`;
 
 function listenForCrash(win) {
   function listener(event) {