[JVM IR] Unmute fixed test

compiler/testData/codegen/box/closures/capturedVarsOptimization/kt17588.kt

@@ -1,4 +1,3 @@
-// IGNORE_BACKEND: JVM_IR
 //WITH_RUNTIME
 class Test {
 
@@ -28,4 +27,4 @@ fun box(): String {
     Test()
 
     return "OK"
-}
+}