kubernetes-helm: 2.9.0 -> 2.9.1 (#42113)

Semi-automatic update generated by https://github.com/ryantm/nixpkgs-update tools.

This update was made based on information from https://repology.org/metapackage/helm/versions.

These checks were done:

- built on NixOS
- /nix/store/clpdnyjaysh2i2h1xjilxryzzb5ywp7y-helm-2.9.1/bin/helm passed the binary check.
- 1 of 1 passed binary check by having a zero exit code.
- 0 of 1 passed binary check by having the new version present in output.
- found 2.9.1 with grep in /nix/store/clpdnyjaysh2i2h1xjilxryzzb5ywp7y-helm-2.9.1
- directory tree listing: https://gist.github.com/ed779ecaf62619059b08a121472e6a96
- du listing: https://gist.github.com/2621c9acfcbf3fa34c093d8bbd9d0292