FIR: Unignore all blackbox tests on context receivers

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

@@ -1,9 +1,7 @@
 // !LANGUAGE: +ContextReceivers
 // TARGET_BACKEND: JVM_IR
-// IGNORE_BACKEND_FIR: JVM_IR
 // WITH_COROUTINES
 // WITH_STDLIB
-// FIR status: context receivers aren't yet supported
 
 import helpers.*
 import kotlin.coroutines.*
@@ -36,4 +34,4 @@ fun box(): String {
     }
 
     return result
-}
+}