Increase timing windows for inattentive sleep warning test

`testInattentiveSleep_warningTiming` is flaky.
It depends on how quickly adb shell commands execute and return.
This CL loosens the timing checks, so that conditions have more time to
stabilize, reducing flakiness of the test.

Bug: 149008991
Test: atest InattentiveSleepTests#testInattentiveSleep_warningTiming
Change-Id: If4a5a09c7bfc6e356609d66f5b94de0770c9713d