Fix return type of private members that return anonymous object

#KT-16813 Fixed

Anonymous objects returned from private-in-file members should behave as for private class members

compiler/testData/diagnostics/tests/subtyping/topLevelAnonymousObjects.kt

@@ -1,6 +1,5 @@
 private var x = object {}
 
 fun test() {
-    // No error, because the type of x is normalized to Any
-    x = object {}
+    x = <!TYPE_MISMATCH!>object<!> {}
 }