Reformat Item ctor and simplify toString

Kotlin/src/main/kotlin/com/gildedrose/Item.kt

@@ -1,7 +1,9 @@
 package com.gildedrose
 
-open class Item(var name: String, var sellIn: Int, var quality: Int) {
-    override fun toString(): String {
-        return this.name + ", " + this.sellIn + ", " + this.quality
-    }
+open class Item(
+    var name: String,
+    var sellIn: Int,
+    var quality: Int,
+) {
+    override fun toString(): String = "$name, $sellIn, $quality"
 }