The jump table assembler is implemented on all architectures now, so
remove the default code. It would be untested otherwise.

R=mstarzinger@chromium.org

Change-Id: I45e42fc04ebb3bb07d975648b1498e2ea4e757d4
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1796328
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#63682}