Use DS_ANALYZER_IMAGE for QA

What does this MR do?

Use DS_ANALYZER_IMAGE when triggering the pipeline of the test projects, instead of custom CI variables. This simplifies the CI configuration of the test projects.

What are the relevant issue numbers?

gitlab-org/gitlab#241976 (closed)

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
  • Tested manually, see comment
• 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