[JS BE] mutes tests for JS_IR_ES6, which muted for JS_IR

js/js.translator/testData/box/expression/function/mangling.kt

@@ -1,4 +1,5 @@
 // IGNORE_BACKEND: JS_IR
+// IGNORE_BACKEND: JS_IR_ES6
 // KJS_WITH_FULL_RUNTIME
 // SKIP_MINIFICATION
 // This test uses eval to access root package, therefore DCE can't infer usage of corresponding functions

js/js.translator/testData/box/expression/function/manglingAnyMethods.kt

@@ -1,4 +1,5 @@
 // IGNORE_BACKEND: JS_IR
+// IGNORE_BACKEND: JS_IR_ES6
 // EXPECTED_REACHABLE_NODES: 1333
 package foo
 

js/js.translator/testData/box/expression/function/manglingClashFunctionsAndClasses.kt

@@ -1,4 +1,5 @@
 // IGNORE_BACKEND: JS_IR
+// IGNORE_BACKEND: JS_IR_ES6
 // SKIP_MINIFICATION
 // This test uses eval, so DCE becomes impossible
 // MODULE: lib