KT-47101: Fix companion supertypes

compiler/testData/diagnostics/tests/scopes/classHeader/companionNestedVsOuter.kt

@@ -0,0 +1,8 @@
+// FIR_IDENTICAL
+open class B
+
+class A {
+    companion object : B() { // Nested B should be invisible here but it's not
+        class B
+    }
+}