JS IR: muted newly failing tests

compiler/testData/codegen/box/defaultArguments/function/complexInheritance.kt

@@ -1,3 +1,4 @@
+// IGNORE_BACKEND: JS_IR
 // See KT-21968
 
 interface A {

compiler/testData/codegen/box/defaultArguments/signature/kt9924.kt

@@ -1,3 +1,4 @@
+// IGNORE_BACKEND: JS_IR
 abstract class A<T> {
     abstract fun test(a: T, b:Boolean = false) : String
 }