A proper modality calculation was missing in IR fake override construction algorithm

#KT-41765 Fixed

compiler/testData/codegen/box/ir/kt41765.kt

@@ -0,0 +1,25 @@
+// MODULE: lib
+// FILE: lib.kt
+
+// KT-41765
+
+interface X {
+    override fun toString() :String
+}
+
+interface Y
+
+abstract class A: Y, X
+
+// MODULE: main(lib)
+// FILE: main.kt
+
+class B: A() {
+    override fun toString() = "BBB"
+}
+
+fun box(): String {
+    if (B().toString() == "BBB") return "OK"
+    return "FAIL"
+}
+