[K/JS] Include jsFirEs6Test into jsFirCompilerTest tests

compiler/testData/codegen/box/defaultArguments/useNextParamInLambdaTailrec.kt

@@ -1,6 +1,6 @@
 // LANGUAGE: -ProhibitIllegalValueParameterUsageInDefaultArguments
 // IGNORE_BACKEND: JVM
-// IGNORE_BACKEND_K2: JVM_IR, JS_IR, NATIVE, WASM
+// IGNORE_BACKEND_K2: JVM_IR, JS_IR, JS_IR_ES6, NATIVE, WASM
 // FIR status: don't support legacy feature. UNINITIALIZED_PARAMETER y. See KT-49800
 tailrec fun foo(x: () -> String? = { y }, y: String = "fail"): String? {
     if (y == "start")