[Tiger] Remove @PlatinumTest for testUninstallFromWorkspace so that the

flaky test runs and we can get a screen record.

Apologies. I didn't realize how @PlatinumTest runs. Apparently demotion
from platinum test list as of Aug 7th cl/554505521 makes them not run.

Bug: b/293944634
Flag: No flag needed. Test only change.
Test: No test needed. Purposefully turning on known flaky test for tracking.
Change-Id: I3aee2d135bcaf64c35c242b580a92ce538b95896