Generating release notes using Pull Request data source is not working

When I use "prs" data source in my `.grenrc.js` file, it recognizing the correct number of closed Pull Requests but does not actually pull any data from them. I get this on my release notes: `No changelog for this release.`

The same when ran with "commits" data source, works fine and lists all the commits that occured for that tag.

Am I missing something ?

首先使用 `.grenrc.js` 中的 `prs` 数据源复现 release notes 的生成，然后将其与正常工作的 `commits` 数据源进行比较。跟踪已关闭的 pull request 是如何被识别并转换为 release note 数据的，并将 `No changelog for this release.` 输出作为失败条件。完成的标准是 `prs` 数据源列出该 tag 的 pull request 数据。

由索引模型根据 Issue 内容生成。