LibJS: Set Array length attributes to "Configurable | Writable"

Libraries/LibJS/Runtime/Array.cpp

@@ -42,7 +42,7 @@ Array* Array::create(GlobalObject& global_object)
 Array::Array(Object& prototype)
     : Object(&prototype)
 {
-    put_native_property("length", length_getter, length_setter);
+    put_native_property("length", length_getter, length_setter, Attribute::Configurable | Attribute::Writable);
 }
 
 Array::~Array()