Bump @azure/identity from 2.1.0 to 4.2.1

Bumps [@azure/identity](https://github.com/Azure/azure-sdk-for-js) from 2.1.0 to 4.2.1.
- [Release notes](https://github.com/Azure/azure-sdk-for-js/releases)
- [Changelog](https://github.com/Azure/azure-sdk-for-js/blob/main/documentation/Changelog-for-next-generation.md)
- [Commits](https://github.com/Azure/azure-sdk-for-js/compare/@azure/identity_2.1.0...@azure/identity_4.2.1)

---
updated-dependencies:
- dependency-name: "@azure/identity"
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>