LibJS: Change Value::to_object(Heap& -> Interpreter&)

Passing a Heap& to it only to then call interpreter() on that is weird.
Let's just give it the Interpreter& directly, like some of the other
to_something() functions.

Libraries/LibJS/Runtime/Function.cpp

@@ -60,7 +60,7 @@ BoundFunction* Function::bind(Value bound_this_value, Vector<Value> arguments)
             // FIXME: Null or undefined should be passed through in strict mode.
             return &interpreter().global_object();
         default:
-            return bound_this_value.to_object(interpreter().heap());
+            return bound_this_value.to_object(interpreter());
         }
     }();