rubocops: add `unless_multiple_conditions`

Library/Homebrew/build.rb

Library/Homebrew/cask/audit.rb

Library/Homebrew/cask/cmd/upgrade.rb

Library/Homebrew/cask/installer.rb

Library/Homebrew/cask/metadata.rb

Library/Homebrew/caveats.rb

Library/Homebrew/cmd/migrate.rb

Library/Homebrew/debrew.rb

Library/Homebrew/deprecate_disable.rb

Library/Homebrew/dev-cmd/bottle.rb

Library/Homebrew/dev-cmd/bump-unversioned-casks.rb

Library/Homebrew/diagnostic.rb

Library/Homebrew/download_strategy.rb

Library/Homebrew/extend/os/mac/keg_relocate.rb

Library/Homebrew/extend/pathname.rb

Library/Homebrew/fetch.rb

Library/Homebrew/formula.rb

Library/Homebrew/formula_installer.rb

Library/Homebrew/formula_pin.rb

Library/Homebrew/keg_relocate.rb