[dagit] Downgrade faker to avoid type warnings
Summary: A recent version bump for faker surfaced type warnings when running Jest tests. Downgrade to 5.2.0 to remove these warnings, since the types haven't caught up yet.
Test Plan: yarn workspace @dagit/core jest
Reviewers: bengotow, prha, sashank
Reviewed By: prha
Differential Revision: https://dagster.phacility.com/D7219