Fix link to /learn/schema (graphql#1809)

Author: benjie

src/pages/learn/index.mdx

@@ -100,6 +100,6 @@ The examples in this guide are based on [a modified version of the SWAPI GraphQL
 
 ## Next steps
 
-Now that you know some key GraphQL concepts, you're ready to learn about all of the different aspects of its [type system](/schema/).
+Now that you know some key GraphQL concepts, you're ready to learn about all of the different aspects of its [type system](/learn/schema/).
 
 For an in-depth learning experience with practical tutorials, see [the available training courses](/community/resources/training-courses).