RuboCop: Remove grace period for silent cop rules

What does this MR do and why?

This MR removes the "grace period" for cops rules added more than two weeks and without any warnings in Slack channel.

This means offenses from these cops are no longer silenced on default branch in CI.

Done via:

  sed -i '/Details: grace period/d' \
     $(git log --name-only --format= -S "Details: grace period" \
       --until "2 weeks ago" .rubocop_todo)

Exceptions

The following cops were kept in "grace period":

• RSpec/ExpectChange because of the upcoming style change in gitlab-org/ruby/gems/gitlab-styles!127 (merged)

How to set up and validate locally

bundle exec rubocop --parallel

# Takes a long time.

or watch the CI job rubocop go 💚

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.