[iOS] Remove ReadingList empty view

This view was used in the old ReadingList implementation.

Bug: none
Cq-Include-Trybots: luci.chromium.try:ios-simulator-cronet;luci.chromium.try:ios-simulator-full-configs
Change-Id: Id4fa1df5a00f0dd572a2d4951764f422231e3874
Reviewed-on: https://chromium-review.googlesource.com/c/1276966
Reviewed-by: Kurt Horimoto <kkhorimoto@chromium.org>
Commit-Queue: Gauthier Ambard <gambard@chromium.org>
Cr-Commit-Position: refs/heads/master@{#599131}
4 files changed