FIR: Unignore all Fir2IrText tests on context receivers

compiler/testData/ir/irText/declarations/contextReceivers/thisWithCustomLabel.kt

@@ -1,5 +1,4 @@
 // !LANGUAGE: +ContextReceivers
-// IGNORE_BACKEND_FIR: JVM_IR
 
 class A<T>(val a: T)
 class B(val b: Any)
@@ -20,4 +19,4 @@ context(labelAInt@A<Int>, A<String>, labelB@B) val C.p: Int
         this@p.c
         this.c
         return 1
-    }
+    }