[go_router] docs: updated link in navigation.md to correct file path …

…for push_with_shell_route.dart

packages/go_router/doc/navigation.md

@@ -86,8 +86,7 @@ screen along with the shell is placed entirely on top of the current screen.
 ![An animation shows pushing a new screen with the different shell as current screen](https://flutter.github.io/assets-for-api-docs/assets/go_router/push_different_shell.gif)
 
 To try out the behavior yourself, see
-[push_with_shell_route.dart](https://github.com/flutter/packages/blob/main/packages/go_router/example/lib/extra_codec.dart).
-
+[push_with_shell_route.dart](https://github.com/flutter/packages/blob/main/packages/go_router/example/lib/push_with_shell_route.dart).
 
 ## Returning values
 Waiting for a value to be returned: