Bump version 7.8.4

• Diff: https://gitlab.com/gitlab-org/gitlab-qa/-/compare/v7.8.3...009c0612f4facb9c1e2c35dc51899b8081083128

• Release notes:

### Other changes (CI, backstage)

- 755! Skip metrics exports for framework sanity specs

- 756! Update reporting script to update test case and issue titles

• Checklist before merging:

  • Diff link is up-to-date.
  • Based on the diff, lib/gitlab/qa/version.rb is updated, according to SemVer.
  • Release notes are accurate.

• Checklist after merging:

  • Update the release notes for the newly created tag.