Update content/graphql/federation.md

Author: kamilmysliwiec

content/graphql/federation.md

@@ -363,7 +363,7 @@ export class AppModule {}
 
 #### Example
 
-A working example is available [here](https://github.com/nestjs/nest/tree/master/sample/31-graphql-federation-code-first/gateway) in code first mode and [here](https://github.com/nestjs/nest/tree/master/sample/32-graphql-federation-schema-first/gateway) in schema first mode.
+A working example is available [here](https://github.com/nestjs/nest/tree/master/sample/31-graphql-federation-code-first/gateway) for the code first mode and [here](https://github.com/nestjs/nest/tree/master/sample/32-graphql-federation-schema-first/gateway) for the schema first mode.
 
 #### Sharing context