wezterm@nightly: add shell completions

[nauxliu]

#166026 Added the shell completions for wezterm but missed wezterm@nightly

In the following questions <cask> is the token of the cask you're submitting.

After making any changes to a cask, existing or new, verify:

• The submission is for a stable version or documented exception.
• brew audit --cask --online <cask> is error-free.
• brew style --fix <cask> reports no offenses.

Additionally, if adding a new cask:

• Named the cask according to the token reference.
• Checked the cask was not already refused (add your cask's name to the end of the search field).
• brew audit --cask --new <cask> worked successfully.
• HOMEBREW_NO_INSTALL_FROM_API=1 brew install --cask <cask> worked successfully.
• brew uninstall --cask <cask> worked successfully.

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[nauxliu]

I'm uncertain about why this audit check is failing. I've tested the installation locally, and it was successful, with the changes meeting the expected behavior. However, the audit is failing in my local environment as well.

Could someone please help me review what modifications I might have overlooked?