Cache files are not being removed in current pub release

## 🐛 Bug Report

The recent bug fix in the commit #469 does actually fix a serious bug which has been in the library for two years where the cache files are neved cleaned up because the `file.exists()` doesn't point to the correct file. The fix has been merged but the release in pub.dev is missing.

There are several issues about this behaviour that have been reported for quite some time.

#377, #452, #446

@mvanbeusekom Sorry for the ping but I believe this is a serious fix missing.

审查 commit #469，并将当前的 pub.dev 发布版本与已合并的修复进行比较。确认已发布的软件包是否仍缺少缓存文件清理修复；当新的 pub.dev 发布版本包含该修复并解决所报告的缓存行为时，即视为完成。

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