Clarify Fragment#onHiddenChanged() documentation.
Clarify Fragment#onHiddenChanged() documentation.

Prior comment said that fragment was hidden for both true and false
values of hidden.

This is support library version of ag/1116166

Bug:
https://code.google.com/p/android/issues/detail?id=53178

Change-Id: I2f4b5e6f3140caa32b30309624c23018928358ce

AndroidX/androidx,androidx/androidx,androidx/androidx,AndroidX/androidx,aosp-mirror/platform_frameworks_support,AndroidX/androidx,aosp-mirror/platform_frameworks_support,androidx/androidx,androidx/androidx,AndroidX/androidx,androidx/androidx,aosp-mirror/platform_frameworks_support,androidx/androidx,androidx/androidx,androidx/androidx,AndroidX/androidx,AndroidX/androidx,aosp-mirror/platform_frameworks_support,AndroidX/androidx,AndroidX/androidx,aosp-mirror/platform_frameworks_support,androidx/androidx,AndroidX/androidx,androidx/androidx,AndroidX/androidx