fix the import :milestone from adding the group_id

Open Micael Bergeron requested to merge 35580-cannot-import-project-with-milestones into master

What does this MR do?

This fix an import validation error.

Why was this MR needed?

Importing a project that contains issues and milestones was failing with a validation error.

Does this MR meet the acceptance criteria?

What are the relevant issue numbers?

Closes #35580 (moved)

Edited by Micael Bergeron