Replace coveralls with coveralls_reborn

[mishina2228]

Description

Submitting the coverage report to coveralls fails due to coveralls-ruby.
The following log is taken from https://github.com/lsegal/yard/runs/4694550961?check_suite_focus=true:

Coveralls encountered an exception:
NoMethodError
undefined method `coverage' for #<SimpleCov::SourceFile:0x000055a67b90ba88>
Did you mean?  coverage_data
/home/runner/work/yard/yard/vendor/bundle/ruby/2.7.0/gems/coveralls-0.7.2/lib/coveralls/simplecov.rb:50:in `block in format'
/home/runner/work/yard/yard/vendor/bundle/ruby/2.7.0/gems/forwardable-1.3.2/lib/forwardable.rb:238:in `each'
/home/runner/work/yard/yard/vendor/bundle/ruby/2.7.0/gems/forwardable-1.3.2/lib/forwardable.rb:238:in `each'
/home/runner/work/yard/yard/vendor/bundle/ruby/2.7.0/gems/coveralls-0.7.2/lib/coveralls/simplecov.rb:40:in `format'
/home/runner/work/yard/yard/vendor/bundle/ruby/2.7.0/gems/simplecov-0.21.2/lib/simplecov/result.rb:51:in `format!'
/home/runner/work/yard/yard/vendor/bundle/ruby/2.7.0/gems/simplecov-0.21.2/lib/simplecov/configuration.rb:197:in `block in at_exit'
/home/runner/work/yard/yard/vendor/bundle/ruby/2.7.0/gems/simplecov-0.21.2/lib/simplecov.rb:189:in `run_exit_tasks!'
/home/runner/work/yard/yard/vendor/bundle/ruby/2.7.0/gems/simplecov-0.21.2/lib/simplecov.rb:179:in `at_exit_behavior'
/home/runner/work/yard/yard/vendor/bundle/ruby/2.7.0/gems/simplecov-0.21.2/lib/simplecov/defaults.rb:30:in `block in <top (required)>'

This PR is based on lemurheavy/coveralls-ruby#161 and replace coveralls-ruby with coveralls-ruby-reborn.

Completed Tasks

• I have read the Contributing Guide.
• The pull request is complete (implemented / written).
• Git commits have been cleaned up (squash WIP / revert commits).
• I wrote tests and ran bundle exec rake locally (if code is attached to PR).