Enable ci_parallel_remote_includes feature flag

This FF is already enabled on `gitlab.com` and it seems stable.

Related to https://gitlab.com/gitlab-org/gitlab/-/issues/413770

Changelog: performance

config/feature_flags/development/ci_parallel_remote_includes.yml

@@ -5,4 +5,4 @@ rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/413770
 milestone: '16.7'
 type: development
 group: group::pipeline authoring
-default_enabled: false
+default_enabled: true