Remove default configuration from specs

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.

Author: bquorning

spec/rubocop/cop/rspec/capybara/feature_methods_spec.rb

@@ -3,8 +3,6 @@
 RSpec.describe RuboCop::Cop::RSpec::Capybara::FeatureMethods, :config do
   subject(:cop) { described_class.new(config) }
 
-  let(:cop_config) { { 'EnabledMethods' => [] } }
-
   it 'flags violations for `background`' do
     expect_offense(<<-RUBY)
       describe 'some feature' do

spec/rubocop/cop/rspec/empty_line_after_example_spec.rb

@@ -3,8 +3,6 @@
 RSpec.describe RuboCop::Cop::RSpec::EmptyLineAfterExample, :config do
   subject(:cop) { described_class.new(config) }
 
-  let(:cop_config) { { 'AllowConsecutiveOneLiners' => true } }
-
   it 'flags a missing empty line after `it`' do
     expect_offense(<<-RUBY)
       RSpec.describe Foo do

spec/rubocop/cop/rspec/example_wording_spec.rb

@@ -6,8 +6,7 @@
   context 'with configuration' do
     let(:cop_config) do
       {
-        'CustomTransform' => { 'have' => 'has' },
-        'IgnoredWords'    => %w[only really]
+        'IgnoredWords' => %w[only really]
       }
     end