Quarantine flaky tests

Signed-off-by: Rémy Coutable <remy@rymai.me>

ee/spec/features/groups/iterations/user_views_iteration_spec.rb

@@ -81,7 +81,7 @@ RSpec.describe 'User views iteration' do
       end
     end
 
-    context 'when grouping by label' do
+    context 'when grouping by label', quarantine: 'https://gitlab.com/gitlab-org/gitlab/-/issues/323731' do
       before do
         sign_in(user)
 

ee/spec/features/projects/iterations/user_views_iteration_spec.rb

@@ -64,7 +64,7 @@ RSpec.describe 'User views iteration' do
 
     it_behaves_like 'render iteration page'
 
-    context 'when grouping by label' do
+    context 'when grouping by label', quarantine: 'https://gitlab.com/gitlab-org/gitlab/-/issues/323731' do
       it_behaves_like 'iteration report group by label'
     end