Fix broken url in docs (#2829)

## Summary

Easy navigation and easy reading for others

docs/source/essentials/migration.mdx

@@ -90,7 +90,7 @@ Kotlin Gradle scripts and/or transformed queries, or if you encounter a build er
 ### Gradle plugin changes
 
 The plugin has been rewritten in Kotlin to make it more maintainable and have better support for multiple GraphQL endpoints.  Below are the
-main changes. Read [plugin-configuration.md](https://www.apollographql.com/docs/android/gradle/plugin-configuration/) for a reference of the
+main changes. Read [plugin-configuration.md](https://www.apollographql.com/docs/android/essentials/plugin-configuration/) for a reference of the
 different options.
 
 #### New plugin ID