fix(docs): correct Milvus indexer import path in README files

[ferrisz]

What type of PR is this?

fix: A bug fix

Check the PR title.

• This PR title match the format: <type>(optional scope): <description>
• The description of this PR title is user-oriented and clear enough for others to understand.
• Attach the PR updating the user documentation if the current PR requires user awareness at the usage level. User docs repo

(Optional) Translate the PR title into Chinese.

修复: 修复 Milvus Indexer README 中的导入路径错误

(Optional) More detailed description for this PR(en: English/zh: Chinese).

en:
This pull request fixes the incorrect import paths in the Milvus Indexer README documentation. The update ensures that users will be able to compile the code without encountering import errors. The change is confined to the documentation and does not affect any functional aspects of the codebase.

zh(optional):
该 PR 修复了 Milvus Indexer README 文档中错误的包导入路径问题。此次更新确保用户在编译代码时不会遇到导入错误。此次更改仅限于文档，不影响代码库的功能。

(Optional) Which issue(s) this PR fixes:

N/A

(optional) The PR that updates user documentation:

N/A

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}

[meguminnnnnnnnn]

麻烦签署下CLA吧~