[JS IR BE] Minor: Use proper trow in js compiler test runtime

js/js.translator/testData/_commonFiles/fail.kt

@@ -3,9 +3,5 @@ package kotlin
 // see StdLibTestBase.removeAdHocAssertions
 
 fun fail(message: String? = null): Nothing {
-    // TODO: replace with next version when exception is supported properly
-    // throw Exception(message)
-
-    js("throw new Error(message)")
-    null!!
+    throw Exception(message)
 }