[FIR] Properly support smartcasts on stable when subjects in when conditions

^KT-49860 Fixed

compiler/testData/codegen/box/ieee754/smartCastOnWhenSubjectAfterCheckInBranch_properIeeeComparisons.kt

@@ -1,6 +1,4 @@
 // !LANGUAGE: +ProperIeee754Comparisons
-// IGNORE_BACKEND_FIR: JVM_IR
-// FIR status: Fail 1: other
 
 fun testF(x: Any) =
     when (x) {
@@ -24,4 +22,4 @@ fun box(): String {
     if (td != "0.0") return "Fail 2: $td"
 
     return "OK"
-}
+}