Mark an ActivityThreadTest as flaky

Bug: 194242735
Test: Build
Change-Id: I2452db8523438de4d06c938c3c3fa1d8a9aa0f4e
Merged-In: I2452db8523438de4d06c938c3c3fa1d8a9aa0f4e
(cherry picked from commit 0b6ea59fe04899b0d7c2a8c623479f3561129bba)
1 file changed