Re-add property to project_attributes.yml

What does this MR do and why?

This MR fixes a master:broken #352764 (closed).

It re-adds a property removed in !79968 (comment 842371207).

How to set up and validate locally

This test will pass on this branch but fail on master:

FOSS_ONLY=1 bundle exec rspec spec/requests/api/projects_spec.rb:2231

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

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

Related to #352764 (closed)