Include non-root user for spotbugs

What does this MR do?

Use non-root user for spotbugs.

What are the relevant issue numbers?

Use non-root users in SAST analyzers (gitlab-org/gitlab#474602) • Julian Thome, Tal Kopel • 17.6 • On track

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 updated/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