docs: fix fiddle path (#30144)

This is breaking the build in `electron/electronjs.org-new` and will
most likely not work when clicking the "Fiddle" button.

Rel: electron/website#65

Co-authored-by: Antón Molleda <amolleda@gmail.com>

docs/tutorial/launch-app-from-url-in-another-app.md

@@ -168,7 +168,7 @@ After you start your electron app, you can now enter in a URL in your browser th
     can leave it empty.
 -->
 
-```fiddle docs/fiddles/system/protocol-handler/launch-app-from-url-in-another-app
+```fiddle docs/fiddles/system/protocol-handler/launch-app-from-URL-in-another-app
 
 ```