CopyWords, as the name implies, copies raw words anyway, so there
is no need for type specialization.
MoveWords was dead code.

Bug: v8:8238
Change-Id: Ib497cfbabdcf8bac672ac74ef69f679b50ddfd6e
Reviewed-on: https://chromium-review.googlesource.com/c/1316609Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57226}