Fix pipeline job 5046949

What does this MR do and why?

Skip flaky testcase for failed job 5046949: https://jihulab.com/gitlab-cn/gitlab/-/jobs/5046949

RSpec::Retry: 2nd try ./spec/lib/gitlab/analytics/cycle_analytics/median_spec.rb:29
Failures:
  1) Gitlab::Analytics::CycleAnalytics::Median returns median duration seconds as float
     Failure/Error: expect(subject).to be_within(0.5).of(7.5.minutes.seconds)
       expected 449.462518 to be within 0.5 of 450.0 seconds
     # ./spec/lib/gitlab/analytics/cycle_analytics/median_spec.rb:41:in `block (2 levels) in <main>'
     # ./spec/lib/gitlab/analytics/cycle_analytics/median_spec.rb:22:in `block (3 levels) in <main>'
     # ./spec/lib/gitlab/analytics/cycle_analytics/median_spec.rb:22:in `block (2 levels) in <main>'
     # ./spec/spec_helper.rb:413:in `block (3 levels) in <top (required)>'
     # ./spec/support/sidekiq_middleware.rb:9:in `with_sidekiq_server_middleware'
     # ./spec/spec_helper.rb:405:in `block (2 levels) in <top (required)>'
     # ./spec/spec_helper.rb:401:in `block (3 levels) in <top (required)>'
     # ./lib/gitlab/application_context.rb:58:in `with_raw_context'
     # ./spec/spec_helper.rb:401:in `block (2 levels) in <top (required)>'
     # ./spec/spec_helper.rb:241:in `block (2 levels) in <top (required)>'
     # ./spec/support/system_exit_detected.rb:7:in `block (2 levels) in <main>'
     # ./spec/support/flaky_tests.rb:27:in `block (2 levels) in <main>'
     # ./spec/support/database/prevent_cross_joins.rb:106:in `block (3 levels) in <main>'
     # ./spec/support/database/prevent_cross_joins.rb:60:in `with_cross_joins_prevented'
     # ./spec/support/database/prevent_cross_joins.rb:106:in `block (2 levels) in <main>'
     # ./jh/spec/spec_helper.rb:37:in `block (2 levels) in <main>'
Finished in 6.4 seconds (files took 44.25 seconds to load)
1 example, 1 failure
Failed examples:
rspec ./spec/lib/gitlab/analytics/cycle_analytics/median_spec.rb:29 # Gitlab::Analytics::CycleAnalytics::Median returns median duration seconds as float
[TEST PROF INFO] Time spent in factories: 00:02.730 (29.58% of total time)