[Feature flag] Enable ssh_key_expiration_email_notification

changelogs/unreleased/326386-enable-ssh-key-expiration-email-notification.yml

+---
+title: Email users about SSH keys that are expired or expiring soon
+merge_request: 61812
+author:
+type: added

config/feature_flags/development/ssh_key_expiration_email_notification.yml

@@ -5,4 +5,4 @@ rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/326386
 milestone: '13.11'
 type: development
 group: group::compliance
-default_enabled: false
+default_enabled: true