completions: add missing require.

[MikeMcQuaid]

Fixes #22364.

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Done by ✋🏻

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[Copilot]

Pull request overview

This PR fixes brew completions link / brew completions unlink failing with Error: uninitialized constant Homebrew::Completions::Tap by ensuring the Tap implementation is loaded when Homebrew::Completions is required.

Changes:

• Add a missing require "tap" to Library/Homebrew/completions.rb so Tap.installed is available.

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[carlocab]

Done by ✋🏻

shocking

[MikeMcQuaid]

@carlocab 👴🏻 still got it