We do not emit this opcode in the asm.js to wasm translator, hence we do
not need to handle this case in the function body decoder.
Replace it by a DCHECK to catch bugs where we might accidentally emit
the opcode.

R=thibaudm@chromium.org

Change-Id: Ibaa07099f30b871c28e3d3cebae96277f46e3164
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2768619Reviewed-by: Thibaud Michaud <thibaudm@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#73513}