Fix bitmap offloading tests for HSUM.

Use package which is setup correctly for multi-user.

Bug: 414714284
Test: atest
FrameworksUiServicesNotificationTests:com.android.server.notification.NotificationManagerServiceTest#verifyBigPictureBitmapOffloaded[EMPTY]
-- --abi x86_64
Flag: TEST_ONLY

Change-Id: I37cf8328149b40b8c3267a83184cd2bd68a0e4bd