Bug 1543449 - Follow-up to properly clear the password field in the doorhanger. r=intermittent

--HG--
extra : transplant_source : %3E%A1%19%AF%DE%DC%07%82%90S%E1%91N%80%D3s%0A%AA%CF%9C

toolkit/components/passwordmgr/test/browser/browser_notifications_2.js

@@ -35,6 +35,7 @@ add_task(async function test_empty_password() {
     // Synthesize input to empty the field
     passwordTextbox.focus();
     await EventUtils.synthesizeKey("KEY_ArrowRight");
+    await EventUtils.synthesizeKey("KEY_ArrowRight");
     await EventUtils.synthesizeKey("KEY_Backspace");
     await EventUtils.synthesizeKey("KEY_Backspace");