Default enable reevaluate_preexisting_states_on_vulnerability_triage feature flag

What does this MR do and why?

Default-enables the reevaluate_preexisting_states_on_vulnerability_triage feature flag by setting default_enabled: true.

This flag was introduced in !242100 (merged) to re-evaluate pre-existing vulnerability state approval policy rules for open merge requests when a vulnerability is triaged (dismissed/resolved/etc.), so MRs unblock without requiring a new pipeline or push. The feature has been validated on GitLab.com and is ready to be enabled by default.

References

• Introduced by: !242100 (merged)
• Rollout issue: #560563 (closed)

Screenshots or screen recordings

N/A — flag flip only, no UI changes.

How to set up and validate locally

No local setup required. This is a feature flag default change only.

MR acceptance checklist

Evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.