[Enhancement] Do some code optimization.[rocketmq_message_reader.go]

### Search before asking

- [X] I had searched in the [issues](https://github.com/apache/eventmesh/issues?q=is%3Aissue) and found no similar issues.

### Enhancement Request

This issue is a subproject issue of eventmesh. the subproject address is:
https://github.com/apache/eventmesh-go
located at:
eventmesh-go/plugin/connector/rocketmq/convert/rocketmq_message_reader.go line 53,55,58,61

### Describe the solution you'd like


### Are you willing to submit PR?

- [ ] Yes I am willing to submit a PR!

The requested code is in eventmesh-go/plugin/connector/rocketmq/convert/rocketmq_message_reader.go, specifically lines 53, 55, 58, and 61. Start by reviewing that file in the linked eventmesh-go subproject and the screenshots attached to this issue to determine the intended optimization. Done means the requested changes are applied and the subproject's existing checks still pass.

Written by the indexing model from the issue text.