chore(deps): bump github.com/anthropics/anthropic-sdk-go from 1.19.0 to 1.20.0 (#8355)

chore(deps): bump github.com/anthropics/anthropic-sdk-go

Bumps [github.com/anthropics/anthropic-sdk-go](https://github.com/anthropics/anthropic-sdk-go) from 1.19.0 to 1.20.0.
- [Release notes](https://github.com/anthropics/anthropic-sdk-go/releases)
- [Changelog](https://github.com/anthropics/anthropic-sdk-go/blob/main/CHANGELOG.md)
- [Commits](https://github.com/anthropics/anthropic-sdk-go/compare/v1.19.0...v1.20.0)

---
updated-dependencies:
- dependency-name: github.com/anthropics/anthropic-sdk-go
  dependency-version: 1.20.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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