Regenerate rubocop todo files

The rubocop todo files have been regenerated using the command:

`bundle exec rake rubocop:todo:generate`

Nonexistent files and the files with no rubocop offenses have been
removed from the todo list.

The grace period for some cops has been retained as they are failing on
the master branch. The corresponding files for these cops have been
added to their todo files.

The grace period for these cops is safe to remove after 1 week of no
warning in #f_rubocop.
See
https://docs.gitlab.com/ee/development/rubocop_development_guide.html#cop-grace-period.