Do not consider 'expect' class type constructors final

Because even a final expected class can be actualized with an open
actual class and thus have subtypes in the platform code

compiler/frontend/src/org/jetbrains/kotlin/psi/synthetics/SyntheticClassOrObjectDescriptor.kt

@@ -114,7 +114,6 @@ class SyntheticClassOrObjectDescriptor(
 
     private inner class SyntheticTypeConstructor(storageManager: StorageManager) : AbstractClassTypeConstructor(storageManager) {
         override fun getParameters(): List<TypeParameterDescriptor> = emptyList()
-        override fun isFinal(): Boolean = true
         override fun isDenotable(): Boolean = true
         override fun getDeclarationDescriptor(): ClassDescriptor = thisDescriptor
         override fun computeSupertypes(): Collection<KotlinType> = syntheticSupertypes

compiler/frontend/src/org/jetbrains/kotlin/resolve/lazy/descriptors/LazyClassDescriptor.java

@@ -650,11 +650,6 @@ public class LazyClassDescriptor extends ClassDescriptorBase implements ClassDes
             return parameters.invoke();
         }
 
-        @Override
-        public boolean isFinal() {
-            return getModality() == Modality.FINAL;
-        }
-
         @Override
         public boolean isDenotable() {
             return true;