Enable `ci_if_parenthesis_enabled` feature flag

- Add feature flag definition
- Mark it as default enabled

config/feature_flags/development/ci_if_parenthesis_enabled.yml

+---
+name: ci_if_parenthesis_enabled
+introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/37574
+rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/238174
+group: group::ci
+type: development
+default_enabled: true
\ No newline at end of file

doc/ci/variables/README.md

@@ -760,9 +760,9 @@ Examples:
 - `($VARIABLE1 =~ /^content.*/ || $VARIABLE2 =~ /thing$/) && $VARIABLE3`
 - `$CI_COMMIT_BRANCH == "my-branch" || (($VARIABLE1 == "thing" || $VARIABLE2 == "thing") && $VARIABLE3)`
 
-The feature is currently deployed behind a feature flag that is **disabled by default**.
+The feature is currently deployed behind a feature flag that is **enabled by default**.
 [GitLab administrators with access to the GitLab Rails console](../../administration/feature_flags.md)
-can opt to enable it for your instance.
+can opt to disable it for your instance.
 
 To enable it:
 

lib/gitlab/ci/features.rb

@@ -57,7 +57,7 @@ module Gitlab
       end
 
       def self.ci_if_parenthesis_enabled?
-        ::Feature.enabled?(:ci_if_parenthesis_enabled)
+        ::Feature.enabled?(:ci_if_parenthesis_enabled, default_enabled: true)
       end
 
       def self.allow_to_create_merge_request_pipelines_in_target_project?(target_project)