Bump V5 to 5.5.9

What does this MR do?

Follow-up to Remove outdated License Scanning template (!3016 - merged) to release a new version in major 5.

This is necessary to fix the CI config in the daily DB update pipeline that rebuilds old major releases.

What are the relevant issue numbers?

Does this MR meet the acceptance criteria?

• Changelog entry added
• Documentation created/updated for GitLab EE, if necessary
• Documentation created/updated for this project, if necessary
• Documentation reviewed by technical writer or follow-up review issue created
• Tests added for this feature/bug
• Job definition updated, if necessary
  • Auto-DevOps template
  • Job definition example
  • CI Templates
• Conforms to the code review guidelines
• Conforms to the Go guidelines
• Security reports checked/validated by reviewer