[JS IR] Adapt stepping tests for Kotlin/JS

compiler/testData/debug/stepping/variablesWithoutInitializer.kt

@@ -16,14 +16,19 @@ fun box() {
 // those does not seem useful. This is consistent with javac behavior
 // as well. The JVM backend does generate these line numbers.
 
-// EXPECTATIONS
 // EXPECTATIONS JVM
 // test.kt:4 box
 // test.kt:5 box
 // test.kt:6 box
-// EXPECTATIONS
+// EXPECTATIONS JVM JVM_IR
+// test.kt:7 box
+// test.kt:8 box
+// test.kt:9 box
+// test.kt:10 box
+// test.kt:12 box
+
+// EXPECTATIONS JS_IR
 // test.kt:7 box
 // test.kt:8 box
 // test.kt:9 box
 // test.kt:10 box
-// test.kt:12 box