Added for iterator when remove() is present.

compiler/testData/codegen/box/builtinStubMethods/IteratorWithRemove.kt

@@ -0,0 +1,11 @@
+class MyIterator<T>(val v: T): Iterator<T> {
+    override fun next(): T = v
+    override fun hasNext(): Boolean = true
+
+    public fun remove() {}
+}
+
+fun box(): String {
+    (MyIterator<String>("") as MutableIterator<String>).remove()
+    return "OK"
+}