Merge branch...

Merge branch '469101-duo-chat-error-causes-subsequent-chat-to-fail-due-to-consecutive-assistant-messages' into 'master' 

Do not allow repeated roles on Duo Chat to prevent errors

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/157508



Merged-by: Dmitry Gruzd <dgruzd@gitlab.com>
Approved-by: Nathan Weinshenker <nweinshenker@gitlab.com>
Approved-by: Dmitry Gruzd <dgruzd@gitlab.com>
Co-authored-by: lesley <lrazzaghian@gitlab.com>