Bump @modelcontextprotocol/sdk from 1.20.1 to 1.21.0

Bumps [@modelcontextprotocol/sdk](https://github.com/modelcontextprotocol/typescript-sdk) from 1.20.1 to 1.21.0.
- [Release notes](https://github.com/modelcontextprotocol/typescript-sdk/releases)
- [Commits](modelcontextprotocol/typescript-sdk@1.20.1...1.21.0)

---
updated-dependencies:
- dependency-name: "@modelcontextprotocol/sdk"
  dependency-version: 1.21.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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Author: dependabot[bot]