docs: fix typo in open-url API docs (#39513)

* Fix typo in open-url API docs

* Update app.md

docs/api/app.md

@@ -128,9 +128,8 @@ Emitted when the user wants to open a URL with the application. Your application
 set `NSPrincipalClass` to `AtomApplication`.
 
 As with the `open-file` event, be sure to register a listener for the `open-url`
-event early in your application startup to detect if the the application being
+event early in your application startup to detect if the application is being opened to handle a URL.
-is being opened to handle a URL. If you register the listener in response to a
+If you register the listener in response to a `ready` event, you'll miss URLs that trigger the launch of your application.
-`ready` event, you'll miss URLs that trigger the launch of your application.
 
 ### Event: 'activate' _macOS_