Support co-contributor signature for changelog build
Support co-contributor signature for changelog build

Follow https://github.com/rubocop-hq/rubocop/commit/7b54f43.

This PR supports co-contributor signature for changelog build and prevents
the following build error when using `rake changelog:merge` for
co-contributor signature.

```console
Failures:

  1) RuboCop Project Changelog has link definitions for all implicit links
     Failure/Error:
       expect(changelog.include?("[#{name}]: http"))
         .to be(true), "missing a link for #{name}. " \
                       'Please add this link to the bottom of the file.'

       missing a link for @jdufresne. Please add this link to the bottom
       of the file.
     # ./spec/project_spec.rb:277:in `block (4 levels) in
       <top (required)>'
     # ./spec/project_spec.rb:276:in `each'
     # ./spec/project_spec.rb:276:in `block (3 levels) in
       <top (required)>'
     # tasks/spec_runner.rake:32:in `block in run_specs'
     # tasks/spec_runner.rake:44:in `with_encoding'
     # tasks/spec_runner.rake:28:in `run_specs'
     # tasks/spec_runner.rake:116:in `block in <top (required)>'

Finished in 4 minutes 51.7 seconds (files took 4.62 seconds to load)
15455 examples, 1 failure, 14 pending
```

https://github.com/rubocop-hq/rubocop/runs/1782491421

bbatsov/rubocop,tejasbubane/rubocop,tejasbubane/rubocop,maxjacobson/rubocop,maxjacobson/rubocop,rrosenblum/rubocop,rrosenblum/rubocop,maxjacobson/rubocop,bbatsov/rubocop,tejasbubane/rubocop,rrosenblum/rubocop