docs: clarify open-url not preventable (#37573)

docs: clarify open-url not preventable

Co-authored-by: trop[bot] <37223003+trop[bot]@users.noreply.github.com>
Co-authored-by: Shelley Vohr <shelley.vohr@gmail.com>

docs/api/app.md

@@ -127,8 +127,6 @@ Emitted when the user wants to open a URL with the application. Your application
 `Info.plist` file must define the URL scheme within the `CFBundleURLTypes` key, and
 set `NSPrincipalClass` to `AtomApplication`.
 
-You should call `event.preventDefault()` if you want to handle this event.
-
 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
 is being opened to handle a URL. If you register the listener in response to a