removed actions/checkout for PR branch, use gh

[Ludy87]

Description

changes the permission https://github.com/Stirling-Tools/Stirling-PDF/security/code-scanning/104

Checklist

• I have read the Contribution Guidelines
• I have performed a self-review of my own code
• I have attached images of the change if it is UI based
• I have commented my code, particularly in hard-to-understand areas
• If my code has heavily changed functionality I have updated relevant docs on Stirling-PDFs doc repo
• My changes generate no new warnings
• I have read the section Add New Translation Tags (for new translation tags only)