[Doc] Fix incorrect examples in README.md

[koic]

Motivation and Context

This PR fixes incorrect examples in README.md. The block variable could be removed if it is unused, but when presenting an example :server_context should still be shown as a keyword argument.

Fixes #185.

Types of changes

• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)
• [x] Documentation update

Checklist

• [x] I have read the MCP Documentation
• [x] My code follows the repository's style guidelines
• [x] New and existing tests pass locally
• [x] I have added appropriate error handling
• [x] I have added or updated documentation as needed