Enable configure_iac_scanning_via_mr by default

This enables the configure_iac_scanning_via_mr feature flag by default,
thus making the ability to enable IaC scanning via a MR globally
available.

Changelog: added

config/feature_flags/development/configure_iac_scanning_via_mr.yml

@@ -5,4 +5,4 @@ rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/343966
 milestone: '14.5'
 type: development
 group: group::static analysis
-default_enabled: false
+default_enabled: true