Fix broken Zsh completion scripts

[halturin]

Description

current version of zsh_completion/_kerl is invalid. this PR fixes this problem.

[paulo-ferraz-oliveira]

👋, @halturin.

Thanks for this 😄. This issue was introduced by me a few months back (#418). I don't know what kind of tests I did back then 🙃 but we should probably also at least statically check the completion files in CI, if it's somehow possible.

Regarding linking the pr to an issue I don't think it works in the pr title, but since you replaced the pr template (https://github.com/kerl/kerl/blob/master/.github/pull_request_template.md) you probably missed it too.

I'll (hopefully soonish) update the completion files, since they seem outdated in many places, but still have the wip branch locally, not pushed.

I'll approve the CI run and if all's good merge this. 👍

[paulo-ferraz-oliveira]

Yeah, I now remember I already checked using shfmt and shellcheck on the ZSh completion but hit walls, so gave up:

• shfmt: syntax: consider zsh support mvdan/sh#120
• ShellCheck: Support zsh koalaman/shellcheck#809

[paulo-ferraz-oliveira]

Failing check on macos-13, unexplicably ("Update env." step takes 1 min in some workflows, 7 min when failing 😄). Will try to fix it in a separate pull request.