Send SNI to pypi.org in haproxy

What does this MR do?

This MR fixes a broken test that uses haproxy to forward requests to pypi.org. The test was broken because pypi.org now requires clients to send SNI (Server Name Indication) details, which we weren't doing before. The fix involves adding an sni directive to our haproxy.cfg file.

What are the relevant issue numbers?

gitlab-org/gitlab#330256 (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
  • Job definition example
  • CI Templates (to be removed)
  • Vendored CI Templates (also in CE)
  • Ensure that all of the ENV vars supported are propagated to Docker containers upon docker run in job definitions
• Conforms to the code review guidelines
• Security reports checked/validated by reviewer