It seems that RuboCop comes with certain fixes that improve how RuboCop
RSpec works!

After rubocop/rubocop#7970, all specs with
the `:config` metadata by default use the default configuration. So now,
there is often no reason to add a cop's default configuration in specs.

In rubocop/rubocop#7970 the shared context
`config` was updated to include the following:

    let(:cop) do
      cop_class.new(config, cop_options)
               .tap { |cop| cop.processed_source = processed_source }
    end

This is functionally equivalent to what we have all over our specs:

    subject(:cop) { described_class.new(config) }

The downside is that our specs become a less explicit. Actually they now
have a mystery guest, which may be considered a smell.

There is no longer by default a "when configuration is empty" situation
to test. We always have the default configuration when testing.

The existing tests ("should only fail" -> "onlies fail") did not add
much value.