SASTBot: Monthly dependency updates for 17.2

What does this MR do?

• upgrade github.com/stretchr/testify version [v1.8.4 => v1.9.0]

CHANGELOG is generated by SASTBot.

What are the relevant issue numbers?

• 17.2 Secure:Static Analysis (blue) Planning Issue (gitlab-org/gitlab#465143 - 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