[Docs] Installation command in README is incorrect

[nqtw2e]

Description

The installation command in python/README.md does not work:

pip install openapi-sdk  # ❌ This package does not exist on PyPI

After checking PyPI, the correct package name appears to be:

pip install dnse-sdk-openapi  # ✅ Verified on https://pypi.org/project/dnse-sdk-openapi/

Suggested Fix

Update the installation instruction in python/README.md:

- pip install openapi-sdk
+ pip install dnse-sdk-openapi

[thuan1412]

This's issue cost me a ton of tokens for the AI agents to search the lib name on Pypi lol