Default-enable malware advisory sync and ingestion feature flags

What does this MR do and why?

This MR default-enables the sync_malware_advisories and ingest_malware_advisories feature flags so the malware advisory sync runs out of the box, instead of requiring a manual ChatOps toggle per instance. Both flags are promoted from type: wip to type: beta, since a wip flag cannot set default_enabled: true — only beta/ops flags can. Both flags have already been enabled and validated on staging and production via ChatOps; this change makes that the default for all instances, including self-managed and Dedicated.

Changes

• sync_malware_advisories — gates the sync worker and its PDS/offline data fetches. Moved from config/feature_flags/wip/ to config/feature_flags/beta/, type changed to beta, default_enabled set to true.
• ingest_malware_advisories — gates the database upsert of synced advisories into the pm_malware_* tables. Moved from config/feature_flags/wip/ to config/feature_flags/beta/, type changed to beta, default_enabled set to true.

No application code changes — only the two flag definition files.

Testing

• spec/lib/feature/definition_spec.rb passes with both flags in their new beta form.
• Both flags were already validated on staging and production via ChatOps before this change.

Related

• Rollout issue (sync): #604583 (closed)
• Rollout issue (ingest): #604584 (closed)
• Documentation update: !249742 (merged)
• Part of epic &20876

Notes

• The accompanying documentation update is in !249742 (merged). It adds a section to the GitLab advisory database page marking the feature Beta and available on GitLab.com, GitLab Self-Managed, and GitLab Dedicated.