Remove ClipboardHost.GetClipContentDeprecated@3

It's been 8 months since we replaced it with new GetClipContent@4
crrev.com/c/974669
We can also remove code for checking clip data size from
arc_clipboard_bridge.cc

Bug: b:120576847
Test: cheets_ClipboardTest
Change-Id: I6d67e0c8aa9c7769d34104a93b1d4679c4b77b33
Reviewed-on: https://chromium-review.googlesource.com/c/1364593
Reviewed-by: Mattias Nissler <mnissler@chromium.org>
Reviewed-by: Yusuke Sato <yusukes@chromium.org>
Commit-Queue: Satoshi Niwa <niwa@chromium.org>
Cr-Commit-Position: refs/heads/master@{#615027}
3 files changed