Changed extension in parsing test data (jet -> kt)

compiler/testData/psi/examples/array/MutableArray.kt

@@ -0,0 +1,13 @@
+/**
+  These declarations are "shallow" in the sense that they are not really compiled, only the type-checker uses them
+*/
+
+open class ReadOnlyArray<out T> : ISized {
+  [operator] fun get(index : Int) : T
+}
+
+open class WriteOnlyArray<in T> : ISized { // This is needed to keep IIterator's <T> covariant
+  [operator] fun set(index : Int, value : T)
+}
+
+class MutableArray<T> : ReadOnlyArray<T>, WriteOnlyArray<T> {/*...*/}