[dagit] Repair empty-workspace Scheduler table
Summary: This is a table I overlooked while changing our tables to <Table> components. Noticed it while looking at Dagit in an empty workspace.
Test Plan: View /scheduler while in --empty-workspace, verify proper rendering of schedule table.
Reviewers: bengotow, dgibson, johann, prha
Reviewed By: dgibson
Differential Revision: https://dagster.phacility.com/D5093