docs: consistent route for layout groups example (#10710)

Updated route name from /blog to /about to match the directory structure depicted below the explanation in (group) section under Advanced Layouts.

documentation/docs/30-advanced/10-advanced-routing.md

@@ -170,7 +170,7 @@ By default, the _layout hierarchy_ mirrors the _route hierarchy_. In some cases,
 
 ### (group)
 
-Perhaps you have some routes that are 'app' routes that should have one layout (e.g. `/dashboard` or `/item`), and others that are 'marketing' routes that should have a different layout (`/blog` or `/testimonials`). We can group these routes with a directory whose name is wrapped in parentheses — unlike normal directories, `(app)` and `(marketing)` do not affect the URL pathname of the routes inside them:
+Perhaps you have some routes that are 'app' routes that should have one layout (e.g. `/dashboard` or `/item`), and others that are 'marketing' routes that should have a different layout (`/about` or `/testimonials`). We can group these routes with a directory whose name is wrapped in parentheses — unlike normal directories, `(app)` and `(marketing)` do not affect the URL pathname of the routes inside them:
 
 ```diff
 src/routes/