chore: add update for test_message_schema

[jokemanfire]

Motivation and Context

fix ci fail

How Has This Been Tested?

and you can use UPDATE_SCHEMA=1 cargo test -p rmcp --test test_message_schema --features="server client schemars" to update schema file.

Breaking Changes

Types of changes

• 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)
• Documentation update

Checklist

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

Additional context