Quarantine flaky N+1 system test

This test has been failing often and passes upon retry.
It is not clear what changes the expected/actual values
across test runs, as the expected values are dynamic based
on the control value.

spec/features/issuables/issuable_list_spec.rb

@@ -15,7 +15,7 @@ RSpec.describe 'issuable list', :js do
   end
 
   issuable_types.each do |issuable_type|
-    it "avoids N+1 database queries for #{issuable_type.to_s.humanize.pluralize}" do
+    it "avoids N+1 database queries for #{issuable_type.to_s.humanize.pluralize}", quarantine: { issue: 'https://gitlab.com/gitlab-org/gitlab/-/issues/231426' } do
       control_count = ActiveRecord::QueryRecorder.new { visit_issuable_list(issuable_type) }.count
 
       create_issuables(issuable_type)