Enable DAST extra fields feature flag by default

- Amend YAML file
- Add changelog entry

config/feature_flags/development/security_dast_site_profiles_additional_fields.yml

@@ -5,4 +5,4 @@ rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/292897
 milestone: '13.7'
 type: development
 group: group::dynamic analysis
-default_enabled: false
+default_enabled: true

ee/changelogs/unreleased/philipcunningham-enable-additional-fields-feature-flag-by-default-2928.yml

+---
+title: Enable DAST on-demand scan authentication, request headers and excluded URLs
+merge_request: 58859
+author:
+type: added