Mute some FIR->JVM_IR box tests

FIR generates delegated class members incorrectly (with non-substituted
signatures).

compiler/testData/codegen/box/toArray/toArrayFromJava.kt

@@ -1,6 +1,7 @@
 // TARGET_BACKEND: JVM
 // The old backend thinks `toArray(): Array<Int?>` is the same as `toArray(): Array<Any?>`
 // IGNORE_BACKEND: JVM
+// IGNORE_BACKEND_FIR: JVM_IR
 // WITH_RUNTIME
 // FILE: MyListWithCustomToArray.java