Remove completions for pixi

[ruancomelli]

Remove custom completions for pixi.

Closes #937.

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Note

This is my first contribution to this project. I saw #937 and thought it was a good first issue to help with 🙂

[fdncred]

Thanks. We'd probably want the pixi folder removed too.

[ruancomelli]

@fdncred deleting the only file in the pixi directory should be enough to have the directory itself removed from the project - meaning that this PR is enough.
Take a look at the file-tree on my branch: https://github.com/ruancomelli/nu_scripts/tree/remove-pixi-completions/custom-completions - the pixi directory is not there anymore.

[fdncred]

ok, let's see. thanks.