Merge branch 'experiment-ff-null-hypothesis-milestone-added' into 'master'

Add milestone to null_hypothesis experiment feature flag yaml

See merge request gitlab-org/gitlab!51661

config/feature_flags/experiment/null_hypothesis.yml

@@ -2,6 +2,7 @@
 name: null_hypothesis
 introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/45840
 rollout_issue_url:
+milestone: '13.7'
 type: experiment
 group: group::adoption
 default_enabled: false