[tests] Change builder inference tests in accordance with KT-53749 changes

compiler/testData/codegen/box/builderInference/issues/kt63840b.kt

@@ -1,12 +1,9 @@
 // ISSUE: KT-63840
 
 // IGNORE_LIGHT_ANALYSIS
-// IGNORE_BACKEND_K1: ANY
+// IGNORE_BACKEND: ANY
 // REASON: red code (see corresponding diagnostic test)
 
-// IGNORE_BACKEND_K2: JVM_IR
-// REASON: run-time failure (java.lang.ClassCastException: TargetType cannot be cast to DifferentType @ Kt63840bKt$box$1.invoke)
-
 fun box(): String {
     build {
         if (true)