`Array.prototype.at` docs use "code unit" instead of "item"

还没有人认领这个 Issue。

### Acknowledgement

- [x] I acknowledge that issues using this template may be closed without further explanation at the maintainer's discretion.

### Comment

The `@param` tag [here](https://github.com/microsoft/TypeScript/blob/b465fdbfe175304d9b977da137b2c178ae1091d3/src/lib/es2022.array.d.ts#L4) in the docs for `Array.prototype.at` uses the term "code unit" instead of the more appropriate term "item" or "element". It was presumably copied from the docs for `String.prototype.at` [here](https://github.com/microsoft/TypeScript/blob/main/src/lib/es2022.string.d.ts#L4). I'd make a PR but there was an explicit recommendation not to do that for typos.

从 src/lib/es2022.array.d.ts 中 Array.prototype.at 的 @param 文档开始，然后将其与 src/lib/es2022.string.d.ts 进行比较。更新数组文档，使其使用表示数组值的适当术语，并确认声明文件文档保持一致。

由索引模型根据 Issue 内容生成。