Update gosec to 2.9.6

What does this MR do?

This update includes https://github.com/securego/gosec/pull/747, which may fix a crash happening with Gitaly (example build: https://gitlab.com/gitlab-org/gitaly/-/jobs/2003753188).

Use SHA256 so that we can use the published hashes in the checksum.txt file.

What are the relevant issue numbers?

gitlab-org/gitaly!4268 (comment 814254636)

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