Clean up test skips after KT-17137

We need to clean these up since primitive array `is` checks work now

(cherry picked from commit b413e9ef51606c51ebfb21bd7ff646b0fb75470a)

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

@@ -53,9 +53,6 @@ fun foo(a: Any): Int {
 }
 
 fun box(): String {
-    // Only run this test if primitive array `is` checks work (KT-17137)
-    if ((intArrayOf() as Any) is Array<*>) return "OK"
-
     val iA = IntArray(1)
     if (foo(iA) != 1) return "fail int[]"
     val sA = ShortArray(1)