fix another link to the tutorial (#6390)

Author: martinbonnin

docs/source/index.mdx

@@ -32,7 +32,7 @@ This library is designed with Android in mind, but you can use it in any Kotlin
 
 ## Getting started
 
-If you are new to GraphQL, check out [the tutorial](/kotlin/tutorial/00-introduction/) that will guide you through building an Android app using Apollo.
+If you are new to GraphQL, check out [the tutorial](https://www.apollographql.com/tutorials/apollo-kotlin-android-part1) that will guide you through building an Android app using Apollo.
 
 If you'd like to add Apollo Kotlin to an existing project, follow the steps below.