Run flicker tests 3x

We run the flicker tests multiple times to detect CLs that intoruce flakiness early. Currently we run 5 executions of each CUJ. However, due to lab capacity and impact in presubmit times, this CL reduces the repetitions to 3

Bug: 209843622
Test: atest FlickerTests WMShellFlickerTests
Change-Id: I165937fb82953d62c028ffe96a948d0ca00dbbe2