FIR: Unignore all blackbox tests on context receivers

compiler/testData/codegen/box/extensionFunctions/contextReceivers/delegatedPropertiesOperators.kt

@@ -1,7 +1,5 @@
 // !LANGUAGE: +ContextReceivers
 // TARGET_BACKEND: JVM_IR
-// IGNORE_BACKEND_FIR: JVM_IR
-// FIR status: context receivers aren't yet supported
 // WITH_STDLIB
 
 import kotlin.reflect.KProperty
@@ -34,4 +32,4 @@ fun box(): String {
     result.s = "OK"
     val returnValue = result.s
     return if (operationScore == 2) returnValue else "fail"
-}
+}