[iOS] Remove legacy toolbar button visibility

This CL removes the button visibility of the legacy toolbar which has
been removed in a previous CL.

Bug: 800266
Cq-Include-Trybots: luci.chromium.try:ios-simulator-cronet;luci.chromium.try:ios-simulator-full-configs
Change-Id: I7d847599d4720fa6d5a920baa9b5ad468e6e4d32
Reviewed-on: https://chromium-review.googlesource.com/1236654
Reviewed-by: Olivier Robin <olivierrobin@chromium.org>
Commit-Queue: Gauthier Ambard <gambard@chromium.org>
Cr-Commit-Position: refs/heads/master@{#593157}
4 files changed