Add reliable tag to iteration e2e specs

qa/qa/specs/features/ee/browser_ui/2_plan/iterations/assign_group_iteration_spec.rb

 # frozen_string_literal: true
 
 module QA
-  RSpec.describe 'Plan' do
+  RSpec.describe 'Plan', :reliable do
     describe 'Assign Iterations' do
       let!(:iteration) { EE::Resource::GroupIteration.fabricate_via_api! }
 

qa/qa/specs/features/ee/browser_ui/2_plan/iterations/create_group_iteration_spec.rb

 # frozen_string_literal: true
 
 module QA
-  RSpec.describe 'Plan' do
+  RSpec.describe 'Plan', :reliable do
     describe 'Group Iterations' do
       include Support::Dates