Enable optional_code_owners_sections by default

Issue:
https://gitlab.com/gitlab-org/gitlab/-/issues/232995

Merge request:
https://gitlab.com/gitlab-org/gitlab/-/merge_requests/51002

changelogs/unreleased/id-mark-optional_code_owners_sections-as-default.yml

+---
+title: Designate optional sections in the codeowners file
+merge_request: 51643
+author:
+type: added

config/feature_flags/development/optional_code_owners_sections.yml

@@ -5,4 +5,4 @@ rollout_issue_url:
 milestone: '13.8'
 type: development
 group: group::source code
-default_enabled: false
+default_enabled: true

ee/app/models/approval_wrapped_code_owner_rule.rb

@@ -22,7 +22,7 @@ class ApprovalWrappedCodeOwnerRule < ApprovalWrappedRule
   end
 
   def section_optional?
-    return false unless Feature.enabled?(:optional_code_owners_sections, project)
+    return false unless Feature.enabled?(:optional_code_owners_sections, project, default_enabled: true)
 
     Gitlab::CodeOwners.optional_section?(project, merge_request.target_branch, section)
   end