[Test] Mute failing FIR BB tests related to MPP

compiler/testData/codegen/box/mangling/internal.kt

@@ -1,3 +1,4 @@
+// IGNORE_BACKEND_FIR: JVM_IR
 // IGNORE_BACKEND: JS_IR
 // IGNORE_BACKEND: JS_IR_ES6
 // MODULE: lib
@@ -36,4 +37,4 @@ fun box(): String {
     if (a.foo != 3) return "fail 4: ${a.foo}"
     if (a.B().foo() != 4) return "fail 5: ${a.B().foo()}"
     return "OK"
-}
+}