docs: fix import method text in create dataset guide

### Description

In the documentation page [Create dataset](https://loop.coze.cn/open/docs/cozeloop/create-dataset), the text above the local data import screenshot says:

> 如果导入方式是 数据更新与追加，你需要确保列映射关系符合预期。

However, the highlighted import method in the screenshot is **全量覆盖**. The text should match the selected import method.

### Expected

The sentence should say:

> 如果导入方式是 全量覆盖，你需要确保列映射关系符合预期。

### Actual

The sentence currently says:

> 如果导入方式是 数据更新与追加，你需要确保列映射关系符合预期。

### Additional context

The product UI option itself appears to be correct: the import method option is labeled `全量覆盖`. This looks like a documentation content typo rather than a frontend runtime issue.

Open the Create dataset documentation page and locate the sentence above the local data import screenshot. Change the import-method wording from 数据更新与追加 to 全量覆盖, then verify that the sentence matches the highlighted screenshot option and the expected text.

Written by the indexing model from the issue text.