Fix node pattern tutorial on `...` matcher
Fix node pattern tutorial on `...` matcher

... actually matches zero or more elements, not one or more:

    > pattern = NodePattern.new('(send nil? :sum $...)')
    > pattern.match(RuboCop::ProcessedSource.new('sum(1,2,3,n)', 2.5).ast)
    => [s(:int, 1), s(:int, 2), s(:int, 3), s(:send, nil, :n)]
    > pattern.match(RuboCop::ProcessedSource.new('sum()', 2.5).ast)
    => []

tdeo/rubocop,jfelchner/rubocop,vergenzt/rubocop,deivid-rodriguez/rubocop,bbatsov/rubocop,bbatsov/rubocop,tejasbubane/rubocop,tdeo/rubocop,panthomakos/rubocop,maxjacobson/rubocop,mikegee/rubocop,panthomakos/rubocop,smakagon/rubocop,panthomakos/rubocop,rrosenblum/rubocop,jmks/rubocop,meganemura/rubocop,tejasbubane/rubocop,deivid-rodriguez/rubocop,tdeo/rubocop,jfelchner/rubocop,meganemura/rubocop,maxjacobson/rubocop,rrosenblum/rubocop,mikegee/rubocop,tejasbubane/rubocop,deivid-rodriguez/rubocop,vergenzt/rubocop,jmks/rubocop,jfelchner/rubocop,mikegee/rubocop,vergenzt/rubocop,rrosenblum/rubocop,jmks/rubocop,maxjacobson/rubocop,smakagon/rubocop,meganemura/rubocop