Draft: Draft: Resolve "Docs feedback: Update semgrep custom rules example due to avoid a bug"

What does this MR do and why?

Update the custom ruleset example for semgrep, as the current docs create a bug.

Screenshots or screen recordings

With example from current docs :

With recommended fix :

How to set up and validate locally

1. Create a project with a simple main.py (no specific code required)
2. Activate SAST : template: Security/SAST.gitlab-ci.yml
3. Implement the example from docs

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #388223 (closed)