Update Code Suggestions category for CODEOWNERS

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/177442



Merged-by: Suzanne Selhorn <sselhorn@gitlab.com>
Approved-by: Suzanne Selhorn <sselhorn@gitlab.com>
Co-authored-by: Vitali Tatarintev <vtatarintev@gitlab.com>