bump-formula-pr: fix missing keyword: args error

[SeekingMeaning]

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Fixes error:

Error: missing keyword: args
Please report this issue:
  https://docs.brew.sh/Troubleshooting
/usr/local/Homebrew/Library/Homebrew/dev-cmd/bump-formula-pr.rb:516:in `check_for_duplicate_pull_requests'
/usr/local/Homebrew/Library/Homebrew/dev-cmd/bump-formula-pr.rb:513:in `check_all_pull_requests'
/usr/local/Homebrew/Library/Homebrew/dev-cmd/bump-formula-pr.rb:131:in `bump_formula_pr'
/usr/local/Homebrew/Library/Homebrew/brew.rb:110:in `<main>'