chore(translations): Update translation for cn

[crrashh1542]

This PR aims to update the Simplified Chinese translations as well as to make it more accurate and official.

Firstly, in some translation items, due to there isn't any explanation in brackets in the translations of other languages, so I removed them likewise, which are listed below:

• 获标星数（star）→ 获标星数
• 累计提交数（commit）→ 累计提交总数

Secondly, because some words (like issue and PR) are that familiar with Chinese programmers, there is no need to add extra explanation, so I removed some explanations and use original words instead in some items which are listed below:

• 指出问题数（issue）→ 提出的 issue 总数
• 拉取请求数（PR）→ 发起的 PR 总数

Thirdly, finding some existing Chinese translation items can be confusing, I changed expressions of them in order to make them more accurate and understandable:

• 贡献于（去年）→ 贡献的项目数（去年）
• 合并的 PR 百分比 → 被合并的 PR 占比

Fourthly, I turned some translation items listed below, which are still written in Traditional Chinese in the upstream branch, into Simplified Chinese:

• 審查的 PR 總數 → 审查的 PR 总数
• 沒有語言數據。→ 没有语言数据。

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