Increase the threshold before starting to autogroup

Too many valid use cases are being autogrouped at the current threshold

Bug: 402725724
Test: GroupHelperTest
Test: NotificationManagerServiceTest
Test: NotificationManagerTest
Flag: EXEMPT bug fix
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:7024417f7fdccf36eac985fc4ca2ba12faa1fdcd)
Merged-In: I4a74a50325ba6f63351a13446871da01267bfec6
Change-Id: I4a74a50325ba6f63351a13446871da01267bfec6