[FIR] Update testdata after introducing FirResolvedErrorReference

compiler/testData/codegen/boxError/semantic/unresolvedFunctionReferece.kt

@@ -1,6 +1,5 @@
 // IGNORE_ERRORS
 // ERROR_POLICY: SEMANTIC
-// IGNORE_BACKEND_K2: JS_IR
 
 // MODULE: lib
 // FILE: t.kt
@@ -18,4 +17,4 @@ fun box(): String {
         return "OK"
     }
     return "FAIL"
-}
+}