Fix PEP when SEC is available

What does this MR do and why?

Fix Pipeline execution policy error: job names must be unique error by ignoring scan execution policies when pipeline execution policy is available.

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

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Before

How to set up and validate locally

1. Create a scan execution policy enforcing a security scan such as SAST.
2. Create a pipeline execution policy creating any job, such as basic job with an echo script.
3. Create a project for that the policies apply with a .gitlab-ci.yml file.
4. Verify that pipeline starts and there's no failure in given projects.

See example group: https://gitlab.com/gitlab-org/govern/security-policies/andys-test-group/reproduce-issue-473112

Related issue: #473112 (closed)