RuboCop: Disable cops related to Ruby 3

What does this MR do and why?

This MR is a follow-up of !98112 (merged) disables cops related to Ruby 3.0.

These cops emit offenses in Ruby 3.0 like https://gitlab.com/gitlab-org/gitlab/-/jobs/3067270864. Creating TODOs would conflict with Ruby 2.7. For time being we disable them only when run in Ruby 3.

Migration plan:

• Generate TODOs for these cops (with Ruby 3.0) right before the switch to Ruby 3.0
• Put these cops back in "grace period" to ensure master stability
• Remove "grace period" after the switch
• Incrementally fix TODOs

Screenshots or screen recordings

Configuration diff for Style/MutableConstant and Style/RedundantFreeze via rubocop --show-cops Style/MutableConstant,Style/RedundantFreeze with Ruby 2.7 and 3.0:

--- cops.27.txt 2022-09-22 15:37:29.340754087 +0200
+++ cops.30.txt 2022-09-22 15:37:15.516967785 +0200
@@ -1,7 +1,7 @@
 # Supports --autocorrect
 Style/MutableConstant:
   Description: Do not assign mutable objects to constants.
-  Enabled: true
+  Enabled: false
   VersionAdded: '0.34'
   VersionChanged: '1.8'
   SafeAutoCorrect: false
@@ -22,7 +22,7 @@
 # Supports --autocorrect
 Style/RedundantFreeze:
   Description: Checks usages of Object#freeze on immutable objects.
-  Enabled: true
+  Enabled: false
   VersionAdded: '0.34'
   VersionChanged: '0.66'

How to set up and validate locally

asdf local ruby 2.7.5
unset REVEAL_RUBOCOP_TODO
bundle exec rubocop --parallel --only Style/MutableConstant,Style/RedundantFreeze

asdf local ruby 3.0.4
unset REVEAL_RUBOCOP_TODO
bundle exec rubocop --parallel

MR acceptance checklist

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