Use correct class type when creating class references

(for e.g. PolymorphicSerializer)

Former class reference may had type arguments in it, which lead to bugs
in JS IR.

Fixes https://github.com/Kotlin/kotlinx.serialization/issues/1072

plugins/kotlin-serialization/kotlin-serialization-compiler/src/org/jetbrains/kotlinx/serialization/compiler/backend/ir/GeneratorHelpers.kt

@@ -429,14 +429,13 @@ interface IrBuilderExtension {
 
     fun createClassReference(classType: KotlinType, startOffset: Int, endOffset: Int): IrClassReference {
         val clazz = classType.toClassDescriptor!!
-        val returnType =
+        val classSymbol = compilerContext.referenceClass(clazz.fqNameSafe) ?: error("Couldn't load class $clazz")
-            kClassTypeFor(TypeProjectionImpl(Variance.INVARIANT, classType))
         return IrClassReferenceImpl(
             startOffset,
             endOffset,
-            returnType.toIrType(),
+            compilerContext.irBuiltIns.kClassClass.starProjectedType,
-            compilerContext.referenceClass(clazz.fqNameSafe) ?: error("Couldn't load class $clazz"),
+            classSymbol,
-            classType.toIrType()
+            classSymbol.starProjectedType
         )
     }