Ladybird/AppKit: Remove explicit application activation

We call [NSApp activateIgnoringOtherApps:YES] to ensure the application
is brought into view and focused when launched from a terminal. But in
a macOS environment, we're better off using the `open` command to launch
the application (in which case, it does take foreground focus).

Ladybird/AppKit/main.mm

@@ -67,7 +67,6 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
                                webdriverContentIPCPath:webdriver_content_ipc_path];
 
     [NSApp setDelegate:delegate];
-    [NSApp activateIgnoringOtherApps:YES];
 
     return event_loop.exec();
 }