[Tiger] Re-adding PlatinumTest annotation

This undoes ag/24559527 as this test is no longer flaky.

Actual PlatinumTest presubmit restoration is done in cl/581071347

Bug: b/293944634
Flag: N/A
Test: Test only change
Change-Id: I605f8911fa3a3658c49642efee8d6166545ae89b