JS: unmute now passing tests and mute test that passed by accident.

compiler/testData/codegen/box/arrays/kt2997.kt

@@ -1,4 +1,6 @@
 //KT-2997 Automatically cast error (Array)
+// IGNORE_BACKEND: JS
+// Unmute when JS implements primitive arrays via TypeArray
 
 fun foo(a: Any): Int {
     if (a is IntArray) {

compiler/testData/codegen/box/arrays/kt7288.kt

@@ -1,6 +1,3 @@
-// TODO: muted automatically, investigate should it be ran for JS or not
-// IGNORE_BACKEND: JS
-
 fun test(b: Boolean): String {
     val a = if (b) IntArray(5) else LongArray(5)
     if (a is IntArray) {