Change return type for iterator method of asList impls for *Array

These objects implement AbstractList that extending MutableCollection.
After type propagation `iterator` of AbstractList become MutableIterator, so it cannot be overriden with immutable Iterator

libraries/tools/kotlin-stdlib-gen/src/templates/SpecialJVM.kt

@@ -167,7 +167,7 @@ fun specialJVM(): List<GenericFunction> {
                 override fun size(): Int = this@asList.size()
                 override fun isEmpty(): Boolean = this@asList.isEmpty()
                 override fun contains(o: Any?): Boolean = this@asList.contains(o as T)
-                override fun iterator(): Iterator<T> = this@asList.iterator()
+                override fun iterator(): MutableIterator<T> = this@asList.iterator() as MutableIterator<T>
                 override fun get(index: Int): T = this@asList[index]
                 override fun indexOf(o: Any?): Int = this@asList.indexOf(o as T)
                 override fun lastIndexOf(o: Any?): Int = this@asList.lastIndexOf(o as T)