Fix project count reported in runner usage email

What does this MR do and why?

This MR fixes the project count reported in runner usage email, given that we now may have multiple rows for the same project. This is because in !140566 (merged) we started breaking down projects by runner type and job status, so when requesting the top 1000 projects, you might get something like:

Part of #426562 (closed)

EE: true

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

Before	After

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.