Add expected report for pipfile-lock branch

What does this MR do?

Add a specific expected report for the pipfile-lock-FREEZE branch of the python-pipenv test project.

This proves that Pipfile.lock is fully supported, and that Gemnasium finds vulnerabilities for the package versions listed in the lock file, and not the latest versions. See gitlab-org/security-products/tests/python-pipenv@8bf4274d

What are the relevant issue numbers?

See gitlab-org/gitlab#11756 (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
• 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