Update nokogiri to fix recent CVEs

What does this MR do and why?

Update nokogiri to fix recent CVEs

The main Gemfile was already up to date so this is really only to please the vulnerability scanners as we ship the correct version with GitLab.

References

Please include cross links to any resources that are relevant to this MR This will give reviewers and future readers helpful context to give an efficient review of the changes introduced.

• Diff of the oldest version we have to the latest one https://my.diffend.io/gems/nokogiri/1.15.2/1.16.7
• Changelog: https://github.com/sparklemotion/nokogiri/blob/main/CHANGELOG.md#v1167--2024-07-27 (fixes and dependency updates since 1.15.2)
• https://gitlab.com/gitlab-org/gitlab/-/security/vulnerabilities/118276407 (one of many instances)
• https://gitlab.com/gitlab-org/gitlab/-/security/vulnerabilities/107174524 (one of many instances)
• https://gitlab.com/gitlab-org/gitlab/-/security/vulnerabilities/111443606 (one of many instances)

MR acceptance checklist

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