Fix ActivityLifecycleSpanHelperTest by resetting AppStartMetrics
#4748
| Job | Run time |
|---|---|
| 4m 11s | |
| 3m 57s | |
| 4m 5s | |
| 4m 11s | |
| 4m 21s | |
| 4m 19s | |
| 4m 8s | |
| 4m 22s | |
| 33m 34s |