Use -1 for ListView CollectionInfo

Talkback is supposed to announce the number of "accessibility" items,
and some views from the adapter may set importance for accessibility
to no. Or one view may contain several children views. This is
consistent with what the recyclerview is currently doing.

Bug: 140313418
Test: after the change, talkback doesn't announce the number of items in
a list. Everything else remains the same.

Change-Id: Id05d96562e523ebd746ac4dbb652b0b15bf366a6