Bump kubernetes from 20.13.0 to 21.7.0 in /perf-tests (#2278)

Bumps [kubernetes](https://github.com/kubernetes-client/python) from 20.13.0 to 21.7.0.
- [Release notes](https://github.com/kubernetes-client/python/releases)
- [Changelog](https://github.com/kubernetes-client/python/blob/master/CHANGELOG.md)
- [Commits](kubernetes-client/python@v20.13.0...v21.7.0)

---
updated-dependencies:
- dependency-name: kubernetes
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

perf-tests/requirements.txt

@@ -1,6 +1,6 @@
 PyYAML==6.0
 requests==2.26.0
-kubernetes==20.13.0
+kubernetes==21.7.0
 pytest==4.4.1
 ipaddress==1.0.23 # >= 1.0.17
 cffi==1.15.0