docs: fix license reference in README to match MIT LICENSE file

[ashishpatel26]

Summary

• The README.md footer claimed the SDK is governed by Anthropic's Commercial Terms of Service, but the repo ships an MIT License (LICENSE file).
• Replaced the incorrect "License and terms" section with a simple MIT license reference pointing to the LICENSE file.

Changes

• README.md: Updated the license section to correctly reference the MIT License instead of Anthropic's Commercial Terms of Service.

Fixes #971