chore: Bump datadog-ci to 5.9.1 to pick up simple-git update

[TalUsvyatsky]

What does this PR do?

datdog-ci had simple-git pinned to an old version. To address a CVE, the pinned version was bumped.

This PR updates datadog-ci so we're not transitively pulling in the old version of simple-git.

Motivation

Testing Guidelines

Additional Notes

Types of changes

• Bug fix
• New feature
• Breaking change
• Misc (docs, refactoring, dependency upgrade, etc.)

Check all that apply

• This PR's description is comprehensive
• This PR contains breaking changes that are documented in the description
• This PR introduces new APIs or parameters that are documented and unlikely to change in the foreseeable future
• This PR impacts documentation, and it has been updated (or a ticket has been logged)
• This PR's changes are covered by the automated tests
• This PR collects user input/sensitive content into Datadog