Bug 1772179 - Port osfile.jsm usage to IOUtils in browser/extensions r=sgalich

Differential Revision: https://phabricator.services.mozilla.com/D153698

browser/extensions/formautofill/test/browser/browser_fathom_cc.js

@@ -192,11 +192,9 @@ add_task(async function test_native_cc_model() {
 });
 
 add_task(async function test_native_cc_model_autofill_repo() {
-  const { OS } = ChromeUtils.import("resource://gre/modules/osfile.jsm");
-
   const path = "fathom/autofill-repo-samples/";
   const dirs = ["validation/", "training/", "testing/"];
-  if (await OS.File.exists(getTestFilePath(path))) {
+  if (await IOUtils.exists(getTestFilePath(path))) {
     // Just to ignore timeout failure while running the test on the local
     requestLongerTimeout(10);