[Sync::USS] Remove EntityData.Clone()

After recent code refactoring and simplification, it is not necessary
anymore to clone EntityData and hence removing the Clone() method.

Bug: 953281
Change-Id: Ifba7faa3a95a2f16d2e686443ff5ce8d10763b74
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1576565
Commit-Queue: Mohamed Amir Yosef <mamir@chromium.org>
Reviewed-by: Mikel Astiz <mastiz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#653954}
4 files changed