Add clarifying comments to rubocop:disables

[issyl0]

• Have you followed the guidelines in our Contributing document?
• Have you checked to ensure there aren't other open Pull Requests for the same change?
• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your changes? Here's an example.
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• Needed for Add a DisableComment Cop #18842.

• I said I’d do this “over Christmas” and it’s no longer Christmas, but I’ve finally done most of it!

• The remaining failures here are as follows. Has anyone got any ideas of good comments for why these disables exist?

cask/artifact/abstract_artifact.rb:58:28: C: Cop/DisableComment: Add a clarifying comment to the RuboCop disable comment
        @@sort_order ||= [ # rubocop:disable Style/ClassVars
                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
download_strategy.rb:711:24: C: Cop/DisableComment: Add a clarifying comment to the RuboCop disable comment
  def initialize(path) # rubocop:disable Lint/MissingSuper
                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
lazy_object.rb:13:5: C: Cop/DisableComment: Add a clarifying comment to the RuboCop disable comment
    # rubocop:disable Naming/MemoizedInstanceVariableName
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

[MikeMcQuaid]

Thanks @issyl0! Left some comments for follow-up PRs but will merge this now to avoid conflicts.

[MikeMcQuaid]

Left some comments for follow-up PRs but will merge this now to avoid conflicts.

Oh, would have done but CI is 🔴 😅