[automerger skipped] Mark an ActivityThreadTest as flaky am: 0492d8febe -s ours

am skip reason: Merged-In I2452db8523438de4d06c938c3c3fa1d8a9aa0f4e with SHA-1 0b6ea59fe0 is already in history

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/15336321

Change-Id: Id3724b62b8d8ffad0eb4aafe6c07abe836d2162a