Fix policy variables in scheduled pipelines

What does this MR do and why?

This MR fixes policy variables in scheduled pipelines. The bug was introduced when we enabled security_policies_variables_precedence by default !139828 (merged), because active_policies_scan_actions_for_project used in variables builder was filtering only for pipeline rules.

MR acceptance checklist

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Before	After

How to set up and validate locally

1. Create a project
2. Create .gitlab-ci.yml:

   build_job:
     script:
       echo 'build'

3. Under Settings -> CI/CD, create a new variable CI_REGISTRY_IMAGE with value citizenstig/dvwa
4. Under Secure -> Policies, create a new policy:

   type: scan_execution_policy
   name: Container scanning with variables
   description: ''
   enabled: true
   actions:
     - scan: container_scanning
       variables:
         CS_IMAGE: '$CI_REGISTRY_IMAGE:${CI_COMMIT_REF_SLUG}-${CI_COMMIT_SHORT_SHA}'
         SECURE_LOG_LEVEL: debug
         CI_DEBUG_TRACE: 'true'
   rules:
     - type: schedule
       cadence: '*/15 * * * *'
       branch_type: default

5. Open rails console and trigger the scheduled build manually:

   Security::OrchestrationPolicyRuleSchedule.last.update_columns next_run_at: 1.minute.ago
   Security::OrchestrationPolicyRuleScheduleWorker.new.perform

6. Go to the new pipeline and verify that variables were set (CI_DEBUG_TRACE should print out all variables)
7. Trigger a pipeline on main and verify that only build_job is present