FIR: Mute test that should be disabled since 1.6

compiler/testData/codegen/box/inference/violatingUpperBoundForSelfType.kt

@@ -1,6 +1,7 @@
 // TARGET_BACKEND: JVM
 // WITH_RUNTIME
 // !DIAGNOSTICS: -UNUSED_PARAMETER -CAST_NEVER_SUCCEEDS
+// IGNORE_BACKEND_FIR: JVM_IR
 
 fun <E : Enum<E>> createMap(enumClass: Class<E>) {}
 
@@ -10,4 +11,4 @@ fun box(): String {
     val enumClass: Class<Enum<*>> = A::class.java as Class<Enum<*>>
     createMap(enumClass)
     return "OK"
-}
+}