Nested collections do not work in Kotlin (server)

Code
```kotlin
@Query
fun foo(bar: List<List<Int?>?>): Int {
     // ...
}
```
Generates this given schema:
```graphql
"Query root"
type Query {
  foo(bar: [Int]!): Int!
}
```
but it should be:
```graphql
"Query root"
type Query {
  foo(bar: [[Int]]!): Int!
}
```
The code works in Java. 