fix typo in routing.mdx (#992)

Author: kindy

src/routes/solid-start/building-your-application/routing.mdx

@@ -138,7 +138,7 @@ This will allow you to create a new route that is not nested under the previous
 |-- routes/                       // example.com
     |-- users/
         |-- index.tsx            // example.com/users
-        |-- projects.tsx         // example.com/projects
+        |-- projects.tsx         // example.com/users/projects
     |-- users(details)/
         |-- [id].tsx            // example.com/users/1
 ```