Unwrap fake override of original

This fixes a couple of verify errors related to the order of supertypes in the
class declaration

compiler/testData/codegen/box/fakeOverride/propertySetter.kt

@@ -0,0 +1,18 @@
+trait T {
+    var result: String
+}
+
+open class A : T {
+    override var result: String
+        get() = ""
+        set(value) {}
+}
+
+class B : A(), T
+class C : T, A()
+
+fun box(): String {
+    B().result = ""
+    C().result = ""
+    return "OK"
+}