Bump azure-identity from 1.17.1 to 1.21.0

Bumps [azure-identity](https://github.com/Azure/azure-sdk-for-python) from 1.17.1 to 1.21.0.
- [Release notes](https://github.com/Azure/azure-sdk-for-python/releases)
- [Changelog](https://github.com/Azure/azure-sdk-for-python/blob/main/doc/esrp_release.md)
- [Commits](Azure/azure-sdk-for-python@azure-identity_1.17.1...azure-identity_1.21.0)

---
updated-dependencies:
- dependency-name: azure-identity
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

requirements.txt

@@ -6,7 +6,7 @@ astroid==2.9.0
 attrs==25.1.0
 azure-common==1.1.28
 azure-core==1.32.0
-azure-identity==1.17.1
+azure-identity==1.21.0
 azure-kusto-data==4.5.1
 azure-kusto-ingest==4.5.1
 azure-mgmt-core==1.5.0