Fix a random test failure for Performance/Sum

The skipped tests fail with the following command:
`bundle exec rspec ./spec/rubocop/cli/autocorrect_spec.rb[1:1] ./spec/rubocop/cop/performance/sum_spec.rb[1:13] --seed 26805`

This is fine to do in the rubocop main repository but here we inject
additional config values that are not restored.

There are some things going on that I don't entirely understand:
* Why only failures in this one file
* Why did koic not manage to reproduce with the exact same seed
* Why did the failures seemingly disappear and reappear without any changes to the code

But regardless, this is more correct

spec/rubocop/cli/autocorrect_spec.rb

@@ -7,10 +7,16 @@
 
   include_context 'mock console output'
 
-  before do
+  # Restore injected config as well
+  around do |ex|
+    previous_config = RuboCop::ConfigLoader.default_configuration
+
     RuboCop::ConfigLoader.default_configuration = nil
     RuboCop::ConfigLoader.default_configuration.for_all_cops['SuggestExtensions'] = false
     RuboCop::ConfigLoader.default_configuration.for_all_cops['NewCops'] = 'disable'
+    ex.call
+  ensure
+    RuboCop::ConfigLoader.default_configuration = previous_config
   end
 
   it 'corrects `Performance/ConstantRegexp` with `Performance/RegexpMatch`' do

spec/rubocop/cop/performance/sum_spec.rb

@@ -271,10 +271,6 @@
               ^{method}^^^^^ Use `sum` instead of `#{method}(&:+)`, unless calling `#{method}(&:+)` on an empty array.
       RUBY
 
-      # FIXME: The following failures in JRuby need to be fixed:
-      # https://github.com/rubocop/rubocop-performance/actions/runs/7013730884/job/19080337215
-      skip('Unexpected JRuby autocorrection test failure needs to be fixed.') if RUBY_ENGINE == 'jruby'
-
       expect_correction(<<~RUBY)
         array.sum
       RUBY
@@ -286,10 +282,6 @@
               ^{method}^^^^ Use `sum` instead of `#{method}(:+)`, unless calling `#{method}(:+)` on an empty array.
       RUBY
 
-      # FIXME: The following failures in JRuby need to be fixed:
-      # https://github.com/rubocop/rubocop-performance/actions/runs/7013730884/job/19080337215
-      skip('Unexpected JRuby autocorrection test failure needs to be fixed.') if RUBY_ENGINE == 'jruby'
-
       expect_correction(<<~RUBY)
         array.sum
       RUBY
@@ -301,10 +293,6 @@
               ^{method}^^^ Use `sum` instead of `#{method}(:+)`, unless calling `#{method}(:+)` on an empty array.
       RUBY
 
-      # FIXME: The following failures in JRuby need to be fixed:
-      # https://github.com/rubocop/rubocop-performance/actions/runs/7013730884/job/19080337215
-      skip('Unexpected JRuby autocorrection test failure needs to be fixed.') if RUBY_ENGINE == 'jruby'
-
       expect_correction(<<~RUBY)
         array.sum
       RUBY
@@ -316,10 +304,6 @@
                   ^{method}^^^^ Use `sum` instead of `#{method}(:+)`.
       RUBY
 
-      # FIXME: The following failures in JRuby need to be fixed:
-      # https://github.com/rubocop/rubocop-performance/actions/runs/7013730884/job/19080337215
-      skip('Unexpected JRuby autocorrection test failure needs to be fixed.') if RUBY_ENGINE == 'jruby'
-
       expect_correction(<<~RUBY)
         [1, 2, 3].sum
       RUBY