bump-formula-pr: --write-only flag should skip PR checks

[botantony]

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--write-only flag already skips PR check but it doesn't happen in check_new_version method:

brew/Library/Homebrew/dev-cmd/bump-formula-pr.rb

Line 155 in 2afbceb

check_pull_requests(formula, tap_remote_repo, state: "open") unless args.write_only?

Fixes Homebrew/discussions#6542

[Copilot]

Pull Request Overview

This PR ensures the --write-only flag consistently skips GitHub pull request checks throughout the bump-formula-pr command. The flag is intended to make file modifications without Git/PR actions, but the check_new_version method was still performing PR duplicate checks even when this flag was set.

• Adds conditional check to skip check_pull_requests call in check_new_version method when --write-only is used

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[MikeMcQuaid]

Thanks!