Follow-up to https://github.com/zed-industries/zed/pull/64139 

Fixes CI flacks like
https://github.com/zed-industries/zed/actions/runs/35351932842/job/105623037967?pr=64405#step:15:7107

Halve the test runtime by avoiding the entire `MultiWorkspace` creation
and redraws.

Release Notes:

- N/A