avro

Bump NUnit3TestAdapter from 4.2.0 to 4.2.1 in /lang/csharp (#1469)

Bumps [NUnit3TestAdapter](https://github.com/nunit/nunit3-vs-adapter) from 4.2.0 to 4.2.1.
- [Release notes](https://github.com/nunit/nunit3-vs-adapter/releases)
- [Commits](https://github.com/nunit/nunit3-vs-adapter/compare/V4.2.0...V4.2.1)

---
updated-dependencies:
- dependency-name: NUnit3TestAdapter
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>