E2E: Add data-testid to Code Suggestions User Table

What does this MR do and why?

This MR adds a data-testid to the code suggestions user table, which will be needed to support developing the E2E tests in the following tasks:

• https://gitlab.com/gitlab-org/customers-gitlab-com/-/issues/6879?work_item_iid=6987
• https://gitlab.com/gitlab-org/customers-gitlab-com/-/issues/6879?work_item_iid=6988

MR acceptance checklist

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• I have evaluated the MR acceptance checklist for this MR.