Update data-loader page to fix typo (#1813)

### 📝 Description
`persistant`, an original word of data-loader page, seems typo of
`persistent`.

### 🔗 Related Issues
N/A

website/versioned_docs/version-6.x.x/server/data-loader/data-loader.md

@@ -7,7 +7,7 @@ Data Loaders are a popular caching pattern from the [JavaScript GraphQL implemen
 using the `DataLoader` and `DataLoaderRegistry`.
 
 Since `graphql-kotlin` allows you to abstract the schema generation and data fetching code, you may not even need
-data loaders if instead you have some persistant cache on your server.
+data loaders if instead you have some persistent cache on your server.
 
 ```kotlin
 class User(val id: ID) {