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

js/js.translator/testData/box/char/topLevelCallables.kt

@@ -2,6 +2,7 @@
 
 // Exported declaration uses non-exportable return type: Char
 // IGNORE_BACKEND: JS_IR
+// IGNORE_BACKEND: JS_IR_ES6
 
 @JsName("foo")
 fun foo(): Char = '1'

js/js.translator/testData/box/char/unboxedCharSpecials.kt

@@ -1,4 +1,5 @@
 // IGNORE_BACKEND: JS_IR
+// IGNORE_BACKEND: JS_IR_ES6
 // EXPECTED_REACHABLE_NODES: 1343
 private inline fun typeOf(x: dynamic): String = js("typeof x").unsafeCast<String>()