Kotlin: Fix syntax for unary constructor when parent has type parameters

[tadfisher]

For the Haskell type

data CursorInput a
  = CursorInputNextPage (Maybe a)
  | CursorInputPreviousPage a
  | CursorInputUnknown

we're generating:

@JsonClassDiscriminator("direction")
@Serializable
sealed class CursorInput<A> {
    @Serializable
    @SerialName("nextPage")
    data class NextPage<A>(val key: A?) : CursorInput<A>()

    @Serializable
    @SerialName("previousPage")
    data class PreviousPage<A>(val key: A) : CursorInput<A>()

    @Serializable
    @SerialName("unknown")
    data object Unknown<A> : CursorInput<A>()
}

when it should be:

@JsonClassDiscriminator("direction")
@Serializable
sealed class CursorInput<A> {
    @Serializable
    @SerialName("nextPage")
    data class NextPage<A>(val key: A?) : CursorInput<A>()

    @Serializable
    @SerialName("previousPage")
    data class PreviousPage<A>(val key: A) : CursorInput<A>()

    @Serializable
    @SerialName("unknown")
    data object Unknown : CursorInput<Nothing>()
}