[FIR] Fix tests for vararg execution order after rebase.

compiler/testData/codegen/box/argumentOrder/kt17691.kt

@@ -17,5 +17,4 @@ fun box(): String {
     foo(*arrayOf({ acc4 += "1" }()), y = { acc4 += "2" }())
 
     return if (acc1 == "12" && acc2 == "21" && acc3 == "21" && acc4 == "12") "OK" else "ERROR"
-    return "OK"
 }

compiler/testData/codegen/box/argumentOrder/kt17691WithEnabledFeature.kt

@@ -1,7 +1,6 @@
 // !LANGUAGE: +UseCorrectExecutionOrderForVarargArguments
 // WITH_RUNTIME
 // KJS_WITH_FULL_RUNTIME
-// IGNORE_BACKEND_FIR: JVM_IR
 
 fun foo(vararg x: Unit, y: Any) {}