[fix] fix bug in WindowFunctionLastData::data, it keeps the first data not the last. (#8536)

WindowFunctionLastData::add should keep the last value,
but current implementation keeps the first one.
Obviously, this code is copied from WindowFunctionFirstData::add.

be/src/vec/aggregate_functions/aggregate_function_window.h

@@ -358,9 +358,6 @@ struct WindowFunctionLastData : Data {
         this->set_value(columns, frame_end - 1);
     }
     void add(int64_t row, const IColumn** columns) {
-        if (this->has_set_value()) {
-            return;
-        }
         this->set_value(columns, row);
     }
     static const char* name() { return "last_value"; }