Fix an error when running `rake new_cop`
Fix an error when running `rake new_cop`

Follow up to rubocop/rubocop#10109.

This commit fixes the following error.

```console
% bundle exec rake new_cop\[Department/CustomCop\]
rake aborted!
ArgumentError: wrong number of arguments (given 2, expected 1)
/Users/koic/src/github.com/rubocop/rubocop-rspec/Rakefile:82:in `new'
/Users/koic/src/github.com/rubocop/rubocop-rspec/Rakefile:82:in `block in <top (required)>'
/Users/koic/.rbenv/versions/3.0.2/bin/bundle:23:in `load'
/Users/koic/.rbenv/versions/3.0.2/bin/bundle:23:in `<main>'
Tasks: TOP => new_cop
(See full trace by running task with --trace)
```

nevir/rubocop-rspec,backus/rubocop-rspec,backus/rubocop-rspec,bquorning/rubocop-rspec